Shrinkify libcalls: use float versions of double libm functions with fast-math (bug 17850)
When a call to a double-precision libm function has fast-math semantics
(via function attribute for now because there is no IR-level FMF on calls),
we can avoid fpext/fptrunc operations and use the float version of the call
if the input and output are both float.
We already do this optimization using a command-line option; this patch just
adds the ability for fast-math to use the existing functionality.
I moved the cl::opt from InstructionCombining into SimplifyLibCalls because
it's only ever used internally to that class.
Modified the existing test cases to use the unsafe-fp-math attribute rather
than repeating all tests.
This patch should solve: http://llvm.org/bugs/show_bug.cgi?id=17850
Differential Revision: http://reviews.llvm.org/D5893
llvm-svn: 220390
diff --git a/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp b/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
index c3e2f3a..caae06c 100644
--- a/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
@@ -40,6 +40,13 @@
ColdErrorCalls("error-reporting-is-cold", cl::init(true), cl::Hidden,
cl::desc("Treat error-reporting calls as cold"));
+static cl::opt<bool>
+ EnableUnsafeFPShrink("enable-double-float-shrink", cl::Hidden,
+ cl::init(false),
+ cl::desc("Enable unsafe double to float "
+ "shrinking for math lib calls"));
+
+
//===----------------------------------------------------------------------===//
// Helper Functions
//===----------------------------------------------------------------------===//
@@ -1989,6 +1996,20 @@
IRBuilder<> Builder(CI);
bool isCallingConvC = CI->getCallingConv() == llvm::CallingConv::C;
+ // Command-line parameter overrides function attribute.
+ if (EnableUnsafeFPShrink.getNumOccurrences() > 0)
+ UnsafeFPShrink = EnableUnsafeFPShrink;
+ else if (Callee->hasFnAttribute("unsafe-fp-math")) {
+ // FIXME: This is the same problem as described in optimizeSqrt().
+ // If calls gain access to IR-level FMF, then use that instead of a
+ // function attribute.
+
+ // Check for unsafe-fp-math = true.
+ Attribute Attr = Callee->getFnAttribute("unsafe-fp-math");
+ if (Attr.getValueAsString() == "true")
+ UnsafeFPShrink = true;
+ }
+
// Next check for intrinsics.
if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(CI)) {
if (!isCallingConvC)
@@ -2182,11 +2203,10 @@
}
LibCallSimplifier::LibCallSimplifier(const DataLayout *DL,
- const TargetLibraryInfo *TLI,
- bool UnsafeFPShrink) :
+ const TargetLibraryInfo *TLI) :
DL(DL),
TLI(TLI),
- UnsafeFPShrink(UnsafeFPShrink) {
+ UnsafeFPShrink(false) {
}
void LibCallSimplifier::replaceAllUsesWith(Instruction *I, Value *With) const {