[llvm] r191929 - Pull fptrunc's upwards through selects when one of the select's selectands was a constant. This has a number of benefits, including producing small immediates (easier to materialize, smaller constant pools) as well as being more likely to allow the fptrunc to fuse with a preceding instruction (truncating selects are unusual).
Owen Anderson
resistor at mac.com
Thu Oct 3 14:08:06 PDT 2013
Author: resistor
Date: Thu Oct 3 16:08:05 2013
New Revision: 191929
URL: http://llvm.org/viewvc/llvm-project?rev=191929&view=rev
Log:
Pull fptrunc's upwards through selects when one of the select's selectands was a constant. This has a number of benefits, including producing small immediates (easier to materialize, smaller constant pools) as well as being more likely to allow the fptrunc to fuse with a preceding instruction (truncating selects are unusual).
Modified:
llvm/trunk/lib/Transforms/InstCombine/InstCombineCasts.cpp
llvm/trunk/test/Transforms/InstCombine/fpcast.ll
Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineCasts.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineCasts.cpp?rev=191929&r1=191928&r2=191929&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineCasts.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineCasts.cpp Thu Oct 3 16:08:05 2013
@@ -1229,6 +1229,19 @@ Instruction *InstCombiner::visitFPTrunc(
}
}
+ // (fptrunc (select cond, R1, Cst)) -->
+ // (select cond, (fptrunc R1), (fptrunc Cst))
+ SelectInst *SI = dyn_cast<SelectInst>(CI.getOperand(0));
+ if (SI &&
+ (isa<ConstantFP>(SI->getOperand(1)) ||
+ isa<ConstantFP>(SI->getOperand(2)))) {
+ Value *LHSTrunc = Builder->CreateFPTrunc(SI->getOperand(1),
+ CI.getType());
+ Value *RHSTrunc = Builder->CreateFPTrunc(SI->getOperand(2),
+ CI.getType());
+ return SelectInst::Create(SI->getOperand(0), LHSTrunc, RHSTrunc);
+ }
+
IntrinsicInst *II = dyn_cast<IntrinsicInst>(CI.getOperand(0));
if (II) {
switch (II->getIntrinsicID()) {
Modified: llvm/trunk/test/Transforms/InstCombine/fpcast.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/fpcast.ll?rev=191929&r1=191928&r2=191929&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/fpcast.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/fpcast.ll Thu Oct 3 16:08:05 2013
@@ -31,4 +31,16 @@ define half @test4(float %a) {
ret half %c
}
+; CHECK: test5
+define half @test5(float %a, float %b, float %c) {
+; CHECK: fcmp ogt
+; CHECK: fptrunc
+; CHECK: select
+; CHECK: half 0xH3C00
+ %d = fcmp ogt float %a, %b
+ %e = select i1 %d, float %c, float 1.0
+ %f = fptrunc float %e to half
+ ret half %f
+}
+
declare float @llvm.fabs.f32(float) nounwind readonly
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