More control flow simplifications. (#2673)

* More control flow and Phi param simplifications.

* Fix.

* Fix gcc error.

* Fix.

* More IR cleanup.

* Fix bug in phi param dce + ifelse simplify.

* Propagate and DCE side-effect-free functions.

* Enhance CFG simplifcation to remove loops with no side effects.

* Fix.

* Fixes.

* Fix tests. Add [__AlwaysFoldIntoUseSite] for rayPayloadLocation.

* More cleanup.

* Fixes.

* Fix.

---------

Co-authored-by: Yong He <yhe@nvidia.com>

6 files changed, 125 insertions, 111 deletions

diff --git a/tests/experimental/liveness/liveness-2.slang.expected b/tests/experimental/liveness/liveness-2.slang.expected
index c742fa1fc..16883c1fd 100644
--- a/tests/experimental/liveness/liveness-2.slang.expected
+++ b/tests/experimental/liveness/liveness-2.slang.expected
@@ -51,9 +51,8 @@ layout(local_size_x = 4, local_size_y = 1, local_size_z = 1) in;
 void main()
 {
     int index_0 = int(gl_GlobalInvocationID.x);
-    uint _S4 = uint(index_0);
-    int _S5 = calcThing_0(index_0);
-    ((outputBuffer_0)._data[(_S4)]) = _S5;
+    int _S4 = calcThing_0(index_0);
+    ((outputBuffer_0)._data[(uint(index_0))]) = _S4;
     return;
 }
 
diff --git a/tests/experimental/liveness/liveness-3.slang.expected b/tests/experimental/liveness/liveness-3.slang.expected
index 4dff6b37a..cb093a640 100644
--- a/tests/experimental/liveness/liveness-3.slang.expected
+++ b/tests/experimental/liveness/liveness-3.slang.expected
@@ -53,12 +53,15 @@ int calcThing_0(int offset_0)
         idx_0[0] = 0;
         idx_0[1] = 0;
         idx_0[2] = 0;
+        int _S2 = (k_0 + 7) % 5;
+        bool _S3 = _S2 == 4;
+        int k_1 = k_0 + 1;
         int i_0;
         livenessStart_1(i_0, 0);
         i_0 = 0;
-        int _S2;
-        livenessStart_1(_S2, 0);
-        _S2 = _S1;
+        int _S4;
+        livenessStart_1(_S4, 0);
+        _S4 = _S1;
         for(;;)
         {
             if(i_0 < 17)
@@ -70,74 +73,74 @@ int calcThing_0(int offset_0)
             }
             int modRange_0 = i_0 % 3;
             another_0[i_0 & 1] = another_0[i_0 & 1] + modRange_0;
-            int _S3 = i_0 % 3;
-            int _S4;
-            if(_S3 != 0)
+            int _S5 = i_0 % 3;
+            int _S6;
+            if(modRange_0 != 0)
             {
-                int _S5 = _S2;
-                livenessEnd_0(_S2, 0);
-                int _S6 = _S5 + 1;
-                livenessStart_1(_S4, 0);
-                _S4 = _S6;
+                int _S7 = _S4;
+                livenessEnd_0(_S4, 0);
+                int _S8 = _S7 + 1;
+                livenessStart_1(_S6, 0);
+                _S6 = _S8;
             }
             else
             {
-                int _S7 = _S2;
-                livenessEnd_0(_S2, 0);
-                livenessStart_1(_S4, 0);
-                _S4 = _S7;
+                int _S9 = _S4;
+                livenessEnd_0(_S4, 0);
+                livenessStart_1(_S6, 0);
+                _S6 = _S9;
             }
-            idx_0[modRange_0] = idx_0[modRange_0] + (_S4 + i_0);
+            idx_0[modRange_0] = idx_0[modRange_0] + (_S6 + i_0);
             i_0 = i_0 + 1;
-            livenessStart_1(_S2, 0);
-            int _S8 = _S4;
-            livenessEnd_0(_S4, 0);
-            _S2 = _S8;
+            livenessStart_1(_S4, 0);
+            int _S10 = _S6;
+            livenessEnd_0(_S6, 0);
+            _S4 = _S10;
         }
         livenessEnd_0(i_0, 0);
         livenessEnd_0(_S1, 0);
-        int _S9 = (k_0 + 7) % 5;
-        if(_S9 == 4)
+        livenessEnd_0(k_0, 0);
+        if(_S3)
         {
-            livenessEnd_0(_S2, 0);
+            livenessEnd_0(_S4, 0);
             livenessEnd_1(idx_0, 0);
-            livenessEnd_0(k_0, 0);
             livenessEnd_2(another_0, 0);
             return total_0;
         }
-        int _S10 = idx_0[0] + idx_0[1];
-        int _S11 = idx_0[2];
+        int _S11 = idx_0[0] + idx_0[1];
+        int _S12 = idx_0[2];
         livenessEnd_1(idx_0, 0);
-        int _S12 = _S10 + _S11;
-        int _S13 = total_0;
+        int _S13 = _S11 + _S12;
+        int _S14 = total_0;
         livenessEnd_0(total_0, 0);
-        int total_1 = _S13 + _S12;
-        k_0 = k_0 + 1;
+        int total_1 = _S14 + _S13;
+        livenessStart_1(k_0, 0);
+        k_0 = k_1;
         livenessStart_1(_S1, 0);
-        int _S14 = _S2;
-        livenessEnd_0(_S2, 0);
-        _S1 = _S14;
+        int _S15 = _S4;
+        livenessEnd_0(_S4, 0);
+        _S1 = _S15;
         livenessStart_1(total_0, 0);
         total_0 = total_1;
     }
     livenessEnd_0(_S1, 0);
     livenessEnd_0(k_0, 0);
     livenessEnd_2(another_0, 0);
-    int _S15 = total_0;
+    int _S16 = total_0;
     livenessEnd_0(total_0, 0);
-    return - _S15;
+    return - _S16;
 }
 
-layout(std430, binding = 0) buffer _S16 {
+layout(std430, binding = 0) buffer _S17 {
     int _data[];
 } outputBuffer_0;
 layout(local_size_x = 4, local_size_y = 1, local_size_z = 1) in;
 void main()
 {
     int index_0 = int(gl_GlobalInvocationID.x);
-    uint _S17 = uint(index_0);
-    int _S18 = calcThing_0(index_0);
-    ((outputBuffer_0)._data[(_S17)]) = _S18;
+    uint _S18 = uint(index_0);
+    int _S19 = calcThing_0(index_0);
+    ((outputBuffer_0)._data[(_S18)]) = _S19;
     return;
 }
 
diff --git a/tests/experimental/liveness/liveness-4.slang.expected b/tests/experimental/liveness/liveness-4.slang.expected
index cd97f8057..efc2e3846 100644
--- a/tests/experimental/liveness/liveness-4.slang.expected
+++ b/tests/experimental/liveness/liveness-4.slang.expected
@@ -36,6 +36,9 @@ int calcThing_0(int offset_0)
         {
             break;
         }
+        int _S1 = (k_0 + 7) % 5;
+        bool _S2 = _S1 == 4;
+        int k_1 = k_0 + 1;
         int i_0;
         livenessStart_1(i_0, 0);
         i_0 = 0;
@@ -52,30 +55,30 @@ int calcThing_0(int offset_0)
             i_0 = i_0 + 1;
         }
         livenessEnd_0(i_0, 0);
-        int _S1 = (k_0 + 7) % 5;
-        if(_S1 == 4)
+        livenessEnd_0(k_0, 0);
+        if(_S2)
         {
-            livenessEnd_0(k_0, 0);
             livenessEnd_1(another_0, 0);
             return 1;
         }
-        k_0 = k_0 + 1;
+        livenessStart_1(k_0, 0);
+        k_0 = k_1;
     }
     livenessEnd_0(k_0, 0);
     livenessEnd_1(another_0, 0);
     return -2;
 }
 
-layout(std430, binding = 0) buffer _S2 {
+layout(std430, binding = 0) buffer _S3 {
     int _data[];
 } outputBuffer_0;
 layout(local_size_x = 4, local_size_y = 1, local_size_z = 1) in;
 void main()
 {
     int index_0 = int(gl_GlobalInvocationID.x);
-    uint _S3 = uint(index_0);
-    int _S4 = calcThing_0(index_0);
-    ((outputBuffer_0)._data[(_S3)]) = _S4;
+    uint _S4 = uint(index_0);
+    int _S5 = calcThing_0(index_0);
+    ((outputBuffer_0)._data[(_S4)]) = _S5;
     return;
 }
 
diff --git a/tests/experimental/liveness/liveness-5.slang.expected b/tests/experimental/liveness/liveness-5.slang.expected
index 3693d3fde..e9fe9d652 100644
--- a/tests/experimental/liveness/liveness-5.slang.expected
+++ b/tests/experimental/liveness/liveness-5.slang.expected
@@ -39,6 +39,9 @@ int calcThing_0(int offset_0)
         {
             break;
         }
+        int _S1 = (k_0 + 7) % 5;
+        bool _S2 = _S1 == 4;
+        int k_1 = k_0 + 1;
         int i_0;
         livenessStart_1(i_0, 0);
         i_0 = 0;
@@ -55,17 +58,17 @@ int calcThing_0(int offset_0)
             i_0 = i_0 + 1;
         }
         livenessEnd_0(i_0, 0);
-        int _S1 = total_0;
+        livenessEnd_0(k_0, 0);
+        int _S3 = total_0;
         livenessEnd_0(total_0, 0);
-        int total_1 = _S1 + another_0[k_0 & 1];
-        int _S2 = (k_0 + 7) % 5;
-        if(_S2 == 4)
+        int total_1 = _S3 + another_0[k_0 & 1];
+        if(_S2)
         {
-            livenessEnd_0(k_0, 0);
             livenessEnd_1(another_0, 0);
             return 1;
         }
-        k_0 = k_0 + 1;
+        livenessStart_1(k_0, 0);
+        k_0 = k_1;
         livenessStart_1(total_0, 0);
         total_0 = total_1;
     }
@@ -81,16 +84,16 @@ int calcThing_0(int offset_0)
     return total_0;
 }
 
-layout(std430, binding = 0) buffer _S3 {
+layout(std430, binding = 0) buffer _S4 {
     int _data[];
 } outputBuffer_0;
 layout(local_size_x = 4, local_size_y = 1, local_size_z = 1) in;
 void main()
 {
     int index_0 = int(gl_GlobalInvocationID.x);
-    uint _S4 = uint(index_0);
-    int _S5 = calcThing_0(index_0);
-    ((outputBuffer_0)._data[(_S4)]) = _S5;
+    uint _S5 = uint(index_0);
+    int _S6 = calcThing_0(index_0);
+    ((outputBuffer_0)._data[(_S5)]) = _S6;
     return;
 }
 
diff --git a/tests/experimental/liveness/liveness-6.slang.expected b/tests/experimental/liveness/liveness-6.slang.expected
index 9c3bae815..b661c09bf 100644
--- a/tests/experimental/liveness/liveness-6.slang.expected
+++ b/tests/experimental/liveness/liveness-6.slang.expected
@@ -43,6 +43,10 @@ int calcThing_0(int offset_0)
         livenessStart_0(arr_0, 0);
         arr_0[0] = 2;
         arr_0[1] = 3;
+        int _S1 = k_0 & 1;
+        int _S2 = (k_0 + 7) % 5;
+        bool _S3 = _S2 == 4;
+        int k_1 = k_0 + 1;
         int i_0;
         livenessStart_1(i_0, 0);
         i_0 = 0;
@@ -56,25 +60,24 @@ int calcThing_0(int offset_0)
                 break;
             }
             another_0[i_0 & 1] = another_0[i_0 & 1] + (k_0 + i_0);
-            arr_0[k_0 & 1] = arr_0[k_0 & 1] + i_0;
+            arr_0[_S1] = arr_0[_S1] + i_0;
             i_0 = i_0 + 1;
         }
         livenessEnd_0(i_0, 0);
-        int _S1 = k_0 & 1;
-        int _S2 = total_0;
+        livenessEnd_0(k_0, 0);
+        int _S4 = total_0;
         livenessEnd_0(total_0, 0);
-        int total_1 = _S2 + another_0[_S1];
-        int _S3 = arr_0[_S1];
+        int total_1 = _S4 + another_0[_S1];
+        int _S5 = arr_0[_S1];
         livenessEnd_1(arr_0, 0);
-        int total_2 = total_1 + _S3;
-        int _S4 = (k_0 + 7) % 5;
-        if(_S4 == 4)
+        int total_2 = total_1 + _S5;
+        if(_S3)
         {
-            livenessEnd_0(k_0, 0);
             livenessEnd_1(another_0, 0);
             return 1;
         }
-        k_0 = k_0 + 1;
+        livenessStart_1(k_0, 0);
+        k_0 = k_1;
         livenessStart_1(total_0, 0);
         total_0 = total_2;
     }
@@ -90,16 +93,16 @@ int calcThing_0(int offset_0)
     return total_0;
 }
 
-layout(std430, binding = 0) buffer _S5 {
+layout(std430, binding = 0) buffer _S6 {
     int _data[];
 } outputBuffer_0;
 layout(local_size_x = 4, local_size_y = 1, local_size_z = 1) in;
 void main()
 {
     int index_0 = int(gl_GlobalInvocationID.x);
-    uint _S6 = uint(index_0);
-    int _S7 = calcThing_0(index_0);
-    ((outputBuffer_0)._data[(_S6)]) = _S7;
+    uint _S7 = uint(index_0);
+    int _S8 = calcThing_0(index_0);
+    ((outputBuffer_0)._data[(_S7)]) = _S8;
     return;
 }
 
diff --git a/tests/experimental/liveness/liveness.slang.expected b/tests/experimental/liveness/liveness.slang.expected
index 4a81b8855..06809ffc3 100644
--- a/tests/experimental/liveness/liveness.slang.expected
+++ b/tests/experimental/liveness/liveness.slang.expected
@@ -21,6 +21,7 @@ void livenessEnd_1(spirv_by_reference int _0, spirv_literal int _1);
 int someSlowFunc_0(int a_0)
 {
     uint _S1 = uint(a_0);
+    int _S2 = a_0 * 20;
     uint v_0;
     livenessStart_0(v_0, 0);
     v_0 = _S1;
@@ -29,20 +30,20 @@ int someSlowFunc_0(int a_0)
     i_0 = 0;
     for(;;)
     {
-        if(i_0 < a_0 * 20)
+        if(i_0 < _S2)
         {
         }
         else
         {
             break;
         }
-        uint _S2 = v_0 >> 1;
-        uint _S3 = v_0;
+        uint _S3 = v_0 >> 1;
+        uint _S4 = v_0;
         livenessEnd_0(v_0, 0);
-        uint _S4 = (_S2 | _S3 << 31) * uint(i_0);
+        uint _S5 = (_S3 | _S4 << 31) * uint(i_0);
         int i_1 = i_0 + 1;
         livenessStart_0(v_0, 0);
-        v_0 = _S4;
+        v_0 = _S5;
         i_0 = i_1;
     }
     livenessEnd_1(i_0, 0);
@@ -58,12 +59,12 @@ struct SomeStruct_0
 
 SomeStruct_0 makeSomeStruct_0()
 {
-    const int  _S5[100] = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
-    SomeStruct_0 s_0 = { 0, 0, _S5 };
+    const int  _S6[100] = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
+    SomeStruct_0 s_0 = { 0, 0, _S6 };
     return s_0;
 }
 
-layout(std430, binding = 1) buffer _S6 {
+layout(std430, binding = 1) buffer _S7 {
     int _data[];
 } anotherBuffer_0;
 int doThing_0(SomeStruct_0 s_1)
@@ -73,11 +74,12 @@ int doThing_0(SomeStruct_0 s_1)
 
 int somethingElse_0(inout SomeStruct_0 s_2)
 {
-    s_2.x_0 = s_2.x_0 + 1;
-    return s_2.x_0;
+    int _S8 = s_2.x_0 + 1;
+    s_2.x_0 = _S8;
+    return _S8;
 }
 
-layout(std430, binding = 0) buffer _S7 {
+layout(std430, binding = 0) buffer _S9 {
     int _data[];
 } outputBuffer_0;
 spirv_instruction(id = 256)
@@ -90,6 +92,12 @@ layout(local_size_x = 4, local_size_y = 1, local_size_z = 1) in;
 void main()
 {
     int index_0 = int(gl_GlobalInvocationID.x);
+    const int  _S10[100] = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
+    int _S11 = index_0 & 7;
+    SomeStruct_0 _S12 = makeSomeStruct_0();
+    int v_1 = someSlowFunc_0(index_0);
+    bool _S13 = (v_1 & 256) != 0;
+    int _S14 = v_1 & 3;
     int i_2;
     livenessStart_1(i_2, 0);
     i_2 = 0;
@@ -105,23 +113,20 @@ void main()
         {
             break;
         }
-        int v_1 = someSlowFunc_0(index_0);
         SomeStruct_0 s_3;
         livenessStart_2(s_3, 0);
         SomeStruct_0 t_0;
         livenessStart_2(t_0, 0);
-        SomeStruct_0 _S8 = makeSomeStruct_0();
-        t_0 = _S8;
-        const int  _S9[100] = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
+        t_0 = _S12;
         SomeStruct_0 u_0;
-        if((v_1 & 256) != 0)
+        if(_S13)
         {
-            s_3.x_0 = ((anotherBuffer_0)._data[(uint(v_1 & 3))]);
-            t_0.x_0 = ((anotherBuffer_0)._data[(uint(v_1 & 3))]);
+            s_3.x_0 = ((anotherBuffer_0)._data[(uint(_S14))]);
+            t_0.x_0 = ((anotherBuffer_0)._data[(uint(_S14))]);
             livenessStart_2(u_0, 0);
             u_0.a_1 = 0;
             u_0.x_0 = 0;
-            u_0.c_0 = _S9;
+            u_0.c_0 = _S10;
         }
         else
         {
@@ -129,37 +134,35 @@ void main()
             livenessStart_2(x_1, 0);
             x_1.a_1 = 0;
             x_1.x_0 = 0;
-            x_1.c_0 = _S9;
-            x_1.x_0 = ((anotherBuffer_0)._data[(uint(v_1 & 3))]) + 1;
-            SomeStruct_0 _S10 = x_1;
+            x_1.c_0 = _S10;
+            x_1.x_0 = ((anotherBuffer_0)._data[(uint(_S14))]) + 1;
+            SomeStruct_0 _S15 = x_1;
             livenessEnd_2(x_1, 0);
             livenessStart_2(u_0, 0);
-            u_0 = _S10;
+            u_0 = _S15;
         }
-        s_3.c_0[index_0 & 7] = s_3.c_0[index_0 & 7] + 1;
-        int _S11 = s_3.x_0 + t_0.x_0;
-        SomeStruct_0 _S12 = u_0;
+        s_3.c_0[_S11] = s_3.c_0[_S11] + 1;
+        int _S16 = s_3.x_0 + t_0.x_0;
+        SomeStruct_0 _S17 = u_0;
         livenessEnd_2(u_0, 0);
-        int _S13 = _S11 + _S12.x_0;
-        int _S14 = doThing_0(t_0);
-        int _S15 = _S13 + _S14;
-        int _S16 = somethingElse_0(t_0);
+        int _S18 = _S16 + _S17.x_0 + doThing_0(t_0);
+        int _S19 = somethingElse_0(t_0);
         livenessEnd_2(t_0, 0);
-        int _S17 = _S15 + _S16;
-        int _S18 = s_3.c_0[2];
+        int _S20 = _S18 + _S19;
+        int _S21 = s_3.c_0[2];
         livenessEnd_2(s_3, 0);
-        int _S19 = _S17 + _S18;
-        int _S20 = res_0;
+        int _S22 = _S20 + _S21;
+        int _S23 = res_0;
         livenessEnd_1(res_0, 0);
-        int res_1 = _S20 + _S19;
+        int res_1 = _S23 + _S22;
         i_2 = i_2 + 1;
         livenessStart_1(res_0, 0);
         res_0 = res_1;
     }
     livenessEnd_1(i_2, 0);
-    int _S21 = res_0;
+    int _S24 = res_0;
     livenessEnd_1(res_0, 0);
-    ((outputBuffer_0)._data[(uint(index_0))]) = _S21;
+    ((outputBuffer_0)._data[(uint(index_0))]) = _S24;
     return;
 }