[LibCallSimplifier] don't get fooled by a fake fmin()

rotateright · rotateright · commit fcc7c1a0baf8 · 2016-01-21T20:19:54.000Z
This is similar to the bug/fix: https://llvm.org/bugs/show_bug.cgi?id=26211 http://reviews.llvm.org/rL258325 The fmin() test case reveals another bug caused by sloppy code duplication. It will crash without this patch because fp128 is a valid floating-point type, but we would think that we had matched a function that used doubles. The new helper function can be used to replace similar checks that are used in several other places in this file. llvm-svn: 258428
diff --git a/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp b/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
@@ -953,13 +953,34 @@ static Value *valueHasFloatPrecision(Value *Val) {
   return nullptr;
 }
 
+/// Any floating-point library function that we're trying to simplify will have
+/// a signature of the form: fptype foo(fptype param1, fptype param2, ...).
+/// CheckDoubleTy indicates that 'fptype' must be 'double'.
+static bool matchesFPLibFunctionSignature(const Function *F, unsigned NumParams,
+                                          bool CheckDoubleTy) {
+  FunctionType *FT = F->getFunctionType();
+  if (FT->getNumParams() != NumParams)
+    return false;
+
+  // The return type must match what we're looking for.
+  Type *RetTy = FT->getReturnType();
+  if (CheckDoubleTy ? !RetTy->isDoubleTy() : !RetTy->isFloatingPointTy())
+    return false;
+
+  // Each parameter must match the return type, and therefore, match every other
+  // parameter too.
+  for (const Type *ParamTy : FT->params())
+    if (ParamTy != RetTy)
+      return false;
+
+  return true;
+}
+
 /// Shrink double -> float for unary functions like 'floor'.
 static Value *optimizeUnaryDoubleFP(CallInst *CI, IRBuilder<> &B,
                                     bool CheckRetType) {
   Function *Callee = CI->getCalledFunction();
-  FunctionType *FT = Callee->getFunctionType();
-  if (FT->getNumParams() != 1 || !FT->getReturnType()->isDoubleTy() ||
-      !FT->getParamType(0)->isDoubleTy())
+  if (!matchesFPLibFunctionSignature(Callee, 1, true))
     return nullptr;
 
   if (CheckRetType) {
@@ -997,12 +1018,7 @@ static Value *optimizeUnaryDoubleFP(CallInst *CI, IRBuilder<> &B,
 /// Shrink double -> float for binary functions like 'fmin/fmax'.
 static Value *optimizeBinaryDoubleFP(CallInst *CI, IRBuilder<> &B) {
   Function *Callee = CI->getCalledFunction();
-  FunctionType *FT = Callee->getFunctionType();
-  // Just make sure this has 2 arguments of the same FP type, which match the
-  // result type.
-  if (FT->getNumParams() != 2 || FT->getReturnType() != FT->getParamType(0) ||
-      FT->getParamType(0) != FT->getParamType(1) ||
-      !FT->getParamType(0)->isFloatingPointTy())
+  if (!matchesFPLibFunctionSignature(Callee, 2, true))
     return nullptr;
 
   // If this is something like 'fmin((double)floatval1, (double)floatval2)',
diff --git a/llvm/test/Transforms/InstCombine/double-float-shrink-1.ll b/llvm/test/Transforms/InstCombine/double-float-shrink-1.ll
@@ -364,6 +364,26 @@ define float @max1(float %a, float %b) {
 ; CHECK-NEXT:  ret
 }
 
+; A function can have a name that matches a common libcall,
+; but with the wrong type(s). Let it be.
+
+define float @fake_fmin(float %a, float %b) {
+  %c = fpext float %a to fp128
+  %d = fpext float %b to fp128
+  %e = call fp128 @fmin(fp128 %c, fp128 %d)
+  %f = fptrunc fp128 %e to float
+  ret float %f
+
+; CHECK-LABEL: fake_fmin(
+; CHECK-NEXT:  %c = fpext float %a to fp128
+; CHECK-NEXT:  %d = fpext float %b to fp128
+; CHECK-NEXT:  %e = call fp128 @fmin(fp128 %c, fp128 %d)
+; CHECK-NEXT:  %f = fptrunc fp128 %e to float
+; CHECK-NEXT:  ret float %f
+}
+
+declare fp128 @fmin(fp128, fp128) ; This is not the 'fmin' you're looking for.
+
 declare double @fmax(double, double)
 
 declare double @tanh(double)
