Fix IGC constant folding bug

paigeale · igcbot · commit 2887a020540d · 2021-10-27T03:09:09.000+02:00
There was an issue in how we were Constant folding the f32tof16 GenISA intrinsic.
diff --git a/IGC/Compiler/CustomSafeOptPass.cpp b/IGC/Compiler/CustomSafeOptPass.cpp
@@ -3221,7 +3221,10 @@ Constant* IGCConstProp::ConstantFoldCallInstruction(CallInst* inst)
         {
             if (C0)
             {
-                C = constantFolder.CreateFPTrunc(C0, inst->getType(), llvm::APFloatBase::rmTowardZero);
+                C = constantFolder.CreateFPTrunc(C0, Type::getHalfTy(inst->getContext()), llvm::APFloatBase::rmTowardZero);
+                C = constantFolder.CreateBitCast(C, Type::getInt16Ty(inst->getContext()));
+                C = constantFolder.CreateZExtOrBitCast(C, Type::getInt32Ty(inst->getContext()));
+                C = constantFolder.CreateBitCast(C, inst->getType());
             }
         }
         break;

Original file line number	Diff line number	Diff line change
`@@ -3221,7 +3221,10 @@ Constant* IGCConstProp::ConstantFoldCallInstruction(CallInst* inst)`
`3221`	`3221`	`{`
`3222`	`3222`	`if (C0)`
`3223`	`3223`	`{`
`3224`		`- C = constantFolder.CreateFPTrunc(C0, inst->getType(), llvm::APFloatBase::rmTowardZero);`
	`3224`	`+ C = constantFolder.CreateFPTrunc(C0, Type::getHalfTy(inst->getContext()), llvm::APFloatBase::rmTowardZero);`
	`3225`	`+ C = constantFolder.CreateBitCast(C, Type::getInt16Ty(inst->getContext()));`
	`3226`	`+ C = constantFolder.CreateZExtOrBitCast(C, Type::getInt32Ty(inst->getContext()));`
	`3227`	`+ C = constantFolder.CreateBitCast(C, inst->getType());`
`3225`	`3228`	`}`
`3226`	`3229`	`}`
`3227`	`3230`	`break;`