[SPIRV] Use VectorTimesScalar opcode. (#3737)

* [SPIRV] Use VectorTimesScalar opcode.

* Fix.

2 files changed, 31 insertions, 0 deletions

diff --git a/source/slang/slang-emit-spirv.cpp b/source/slang/slang-emit-spirv.cpp
index 8063975e2..252f0e917 100644
--- a/source/slang/slang-emit-spirv.cpp
+++ b/source/slang/slang-emit-spirv.cpp
@@ -4981,6 +4981,18 @@ struct SPIRVEmitContext
             const auto lVec = as<IRVectorType>(l->getDataType());
             auto r = operands[1];
             const auto rVec = as<IRVectorType>(r->getDataType());
+            if (op == kIROp_Mul && isFloatingPoint)
+            {
+                if (lVec && !rVec)
+                {
+                    return emitInst(parent, instToRegister, SpvOpVectorTimesScalar, type, kResultID, operands);
+                }
+                else if (!lVec && rVec)
+                {
+                    IRInst* newOperands[2] = { operands[1], operands[0] };
+                    return emitInst(parent, instToRegister, SpvOpVectorTimesScalar, type, kResultID, ArrayView<IRInst*>(newOperands, 2));
+                }
+            }
             const auto go = [&](const auto l, const auto r) {
                 return emitInst(parent, instToRegister, opCode, type, kResultID, l, r);
             };
diff --git a/tests/spirv/vector-times-scalar.slang b/tests/spirv/vector-times-scalar.slang
new file mode 100644
index 000000000..fb997d490
--- /dev/null
+++ b/tests/spirv/vector-times-scalar.slang
@@ -0,0 +1,19 @@
+
+//TEST(compute, vulkan):COMPARE_COMPUTE_EX(filecheck-buffer=BUFFER):-vk -compute -output-using-type
+//TEST:SIMPLE(filecheck=CHECK): -target spirv -stage compute -entry computeMain -emit-spirv-directly
+
+//TEST_INPUT:set output = out ubuffer(data=[0 0 0 0], stride=4)
+RWStructuredBuffer<float> output;
+
+// Test that we are able to use the VectorTimesScalar opcode to simplify the resulting spirv.
+
+// CHECK: OpVectorTimesScalar
+
+[numthreads(1,1,1)]
+void computeMain(int3 tid : SV_DispatchThreadID)
+{
+    float3 v = tid + 2.0;
+    float3 v1 = v * 0.5;
+    // BUFFER: 1.0
+    output[0] = v1.x;
+}
\ No newline at end of file