Clean up some behavior of operator% (#1060)

Work on #1059

The `%` operator in the Slang implementation had several issues, and this change tries to address some of them:

* Renamed most occurences of "mod" describing this operator to be "rem" for "remainder" to better match its semantics in HLSL

* Split the operator into distinct integer and floating-point variants (`IRem` and `FRem`) to simplify having different codegen for the two

* Added floating-point variants of `operator%` and `operator%=` to the stdlib.

* Added custom C++ codegen for `kIROp_FRem` such that it maps to the standard C/C++ `remainder()` function

* Added custom GLSL codegen so that `kIROp_FRem` maps to the GLSL `mod()` function (which isn't correct...)

* Added a test case to confirm that D3D11, D3D12, and CPU targets all agree on the definition of floating-point `%`

* Fixed `render-test-tool` to allow a negative integer in a `data=...` specification. This didn't end up being used in the final test, but still seems like a good fix.

* Added a customized baseline for the Vulkan flavor of that test to confirm that we are *not* compiling correctly to SPIR-V just yet

Addressing the correctness of the output for GLSL/SPIR-V will have to come as a later change given that the operation we want is not exposed directly by unextended GLSL.

3 files changed, 37 insertions, 0 deletions

diff --git a/tests/compute/frem.slang b/tests/compute/frem.slang
new file mode 100644
index 000000000..60012ea1e
--- /dev/null
+++ b/tests/compute/frem.slang
@@ -0,0 +1,29 @@
+// frem.slang
+
+//TEST(compute):COMPARE_COMPUTE:
+//TEST(compute):COMPARE_COMPUTE:-cpu
+//TEST(compute):COMPARE_COMPUTE:-vk
+
+// Test uses of floating-point `%` operator.
+
+RWStructuredBuffer<float> gInput;
+//TEST_INPUT:ubuffer(data=[2.0 1.0 5.0 2.0 2.0 -4.0 -5.0 2.0], stride=4):dxbinding(0),glbinding(0),name=gInput
+
+int test(int inVal)
+{
+    float a = gInput[inVal*2];
+    float b = gInput[inVal*2 + 1];
+    return int(a % b);
+}
+
+//TEST_INPUT:ubuffer(data=[0 0 0 0], stride=4):dxbinding(1),glbinding(1),out,name=outputBuffer
+RWStructuredBuffer<int> outputBuffer;
+
+[numthreads(4, 1, 1)]
+void computeMain(uint3 dispatchThreadID : SV_DispatchThreadID)
+{
+	uint tid = dispatchThreadID.x;
+	int inVal = tid;
+	int outVal = test(inVal);
+	outputBuffer[tid] = outVal;
+}
\ No newline at end of file
diff --git a/tests/compute/frem.slang.2.expected.txt b/tests/compute/frem.slang.2.expected.txt
new file mode 100644
index 000000000..f22b9c805
--- /dev/null
+++ b/tests/compute/frem.slang.2.expected.txt
@@ -0,0 +1,4 @@
+0
+1
+FFFFFFFE
+1
diff --git a/tests/compute/frem.slang.expected.txt b/tests/compute/frem.slang.expected.txt
new file mode 100644
index 000000000..bafada4d1
--- /dev/null
+++ b/tests/compute/frem.slang.expected.txt
@@ -0,0 +1,4 @@
+0
+1
+2
+FFFFFFFF