[llvm] [AMDGPU][CodeGenPrepare] Narrow 64 bit math to 32 bit if profitable (PR #130577)

[Nikita Popov via llvm-commits]

================
@@ -8594,6 +8594,68 @@ static bool optimizeBranch(BranchInst *Branch, const TargetLowering &TLI,
   return false;
 }
 
+static bool tryNarrowMathIfNoOverflow(Instruction *I,
+                                      const TargetTransformInfo *TTI,
+                                      const DataLayout &DL) {
+  unsigned Opc = I->getOpcode();
+  Type *OldType = I->getType();
+
+  if (Opc != Instruction::Add && Opc != Instruction::Mul)
+    return false;
+
+  unsigned OrigBit = OldType->getScalarSizeInBits();
+  unsigned MaxBitsNeed = OrigBit;
----------------
nikic wrote:

```suggestion
  unsigned MaxBitsNeeded = OrigBit;
```

https://github.com/llvm/llvm-project/pull/130577