Fix the folding of floating-point math library calls, like sin(infinity),

so that it detects errors on platforms where libm doesn't set errno.
It's still subject to host libm details though.

llvm-svn: 114148

2 files changed, 28 insertions, 2 deletions

diff --git a/llvm/lib/Analysis/ConstantFolding.cpp b/llvm/lib/Analysis/ConstantFolding.cpp
index 0bf7967e83b..69581ba5ecd 100644
--- a/llvm/lib/Analysis/ConstantFolding.cpp
+++ b/llvm/lib/Analysis/ConstantFolding.cpp
@@ -32,6 +32,7 @@
 #include "llvm/Support/MathExtras.h"
 #include <cerrno>
 #include <cmath>
+#include <fenv.h>
 using namespace llvm;
 
 //===----------------------------------------------------------------------===//
@@ -1039,9 +1040,12 @@ llvm::canConstantFoldCallTo(const Function *F) {
 
 static Constant *ConstantFoldFP(double (*NativeFP)(double), double V, 
                                 const Type *Ty) {
+  feclearexcept(FE_ALL_EXCEPT);
   errno = 0;
   V = NativeFP(V);
-  if (errno != 0) {
+  if (errno != 0 ||
+      fetestexcept(FE_DIVBYZERO | FE_UNDERFLOW | FE_OVERFLOW | FE_INVALID)) {
+    feclearexcept(FE_ALL_EXCEPT);
     errno = 0;
     return 0;
   }
@@ -1056,9 +1060,12 @@ static Constant *ConstantFoldFP(double (*NativeFP)(double), double V,
 
 static Constant *ConstantFoldBinaryFP(double (*NativeFP)(double, double),
                                       double V, double W, const Type *Ty) {
+  feclearexcept(FE_ALL_EXCEPT);
   errno = 0;
   V = NativeFP(V, W);
-  if (errno != 0) {
+  if (errno != 0 ||
+      fetestexcept(FE_DIVBYZERO | FE_UNDERFLOW | FE_OVERFLOW | FE_INVALID)) {
+    feclearexcept(FE_ALL_EXCEPT);
     errno = 0;
     return 0;
   }
diff --git a/llvm/test/Transforms/InstCombine/fold-calls.ll b/llvm/test/Transforms/InstCombine/fold-calls.ll
new file mode 100644
index 00000000000..2b11771969f
--- /dev/null
+++ b/llvm/test/Transforms/InstCombine/fold-calls.ll
@@ -0,0 +1,19 @@
+; RUN: opt -instcombine -S < %s | FileCheck %s
+
+; This shouldn't fold, because sin(inf) is invalid.
+; CHECK: @foo
+; CHECK:   %t = call double @sin(double 0x7FF0000000000000)
+define double @foo() {
+  %t = call double @sin(double 0x7FF0000000000000)
+  ret double %t
+}
+
+; This should fold.
+; CHECK: @bar
+; CHECK:   ret double 0x3FDA6026360C2F91
+define double @bar() {
+  %t = call double @sin(double 9.0)
+  ret double %t
+}
+
+declare double @sin(double)