[llvm] Added fix to enable constant folding that is missing for math library functions (scalbln , scalbn, ldexp) (PR #169893)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-transforms

Author: Raja Sudha Sri Harika (Sriharika1506)

<details>
<summary>Changes</summary>

Issue : #<!-- -->112631

This patch adds support for constant folding for certain math library functions wherever it was previously missing.

---
Full diff: https://github.com/llvm/llvm-project/pull/169893.diff


2 Files Affected:

- (modified) llvm/include/llvm/Transforms/Utils/SimplifyLibCalls.h (+3) 
- (modified) llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp (+29) 


``````````diff
diff --git a/llvm/include/llvm/Transforms/Utils/SimplifyLibCalls.h b/llvm/include/llvm/Transforms/Utils/SimplifyLibCalls.h
index 4e7c97194cc59..72b8f4b427b3b 100644
--- a/llvm/include/llvm/Transforms/Utils/SimplifyLibCalls.h
+++ b/llvm/include/llvm/Transforms/Utils/SimplifyLibCalls.h
@@ -214,6 +214,9 @@ class LibCallSimplifier {
   Value *optimizeSymmetric(CallInst *CI, LibFunc Func, IRBuilderBase &B);
   Value *optimizeRemquo(CallInst *CI, IRBuilderBase &B);
   Value *optimizeFdim(CallInst *CI, IRBuilderBase &B);
+
+  Value *foldLdexp(CallInst *CI, IRBuilderBase &B);
+  
   // Wrapper for all floating point library call optimizations
   Value *optimizeFloatingPointLibCall(CallInst *CI, LibFunc Func,
                                       IRBuilderBase &B);
diff --git a/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp b/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
index 4a1565977b91c..7508048d3032e 100644
--- a/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
@@ -2464,6 +2464,24 @@ Value *LibCallSimplifier::optimizePow(CallInst *Pow, IRBuilderBase &B) {
   return nullptr;
 }
 
+Value *LibCallSimplifier::foldLdexp(CallInst *CI,IRBuilderBase &B) {
+
+  Type*RequiredType = CI->getType();
+  if(!RequiredType->isFPOrFPVectorTy())
+    return nullptr;
+
+  Value*x = CI->getArgOperand(0); 
+  Value*exp = CI->getArgOperand(1);
+  Module*M = CI->getModule();
+
+  Function*ldexpDecl = llvm::Intrinsic::getOrInsertDeclaration(M, Intrinsic::ldexp,{RequiredType, exp->getType()});
+  
+  CallInst *NewCall = B.CreateCall(ldexpDecl, {x, exp}, CI->getName());
+  NewCall->setAttributes(CI->getAttributes());
+  return copyFlags(*CI, NewCall);
+}
+
+
 Value *LibCallSimplifier::optimizeExp2(CallInst *CI, IRBuilderBase &B) {
   Module *M = CI->getModule();
   Function *Callee = CI->getCalledFunction();
@@ -4031,6 +4049,17 @@ Value *LibCallSimplifier::optimizeFloatingPointLibCall(CallInst *CI,
   case LibFunc_exp2:
   case LibFunc_exp2f:
     return optimizeExp2(CI, Builder);
+  // New ldexp / scalbn / scalbln family:
+  case LibFunc_ldexp:
+  case LibFunc_ldexpf:
+  case LibFunc_ldexpl:
+  case LibFunc_scalbn:
+  case LibFunc_scalbnf:
+  case LibFunc_scalbnl:
+  case LibFunc_scalbln:
+  case LibFunc_scalblnf:
+  case LibFunc_scalblnl:
+    return foldLdexp(CI, Builder);
   case LibFunc_fabsf:
   case LibFunc_fabs:
   case LibFunc_fabsl:

``````````

</details>


https://github.com/llvm/llvm-project/pull/169893