[InstCombine] Extend saturating idempotent atomicrmw transform to FP

I'm assuming that the nan propogation logic for InstructonSimplify's handling of fadd and fsub is correct, and applying the same to atomicrmw.

Differential Revision: https://reviews.llvm.org/D58836

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@355222 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/InstCombine/InstCombineAtomicRMW.cpp b/lib/Transforms/InstCombine/InstCombineAtomicRMW.cpp
index d3a7d32ec7588cff66c079ec14ee5cb5a04b675f..5f37a00f56cf54334fc91cb8db1d7b5a3634f725 100644 (file)
--- a/lib/Transforms/InstCombine/InstCombineAtomicRMW.cpp
+++ b/lib/Transforms/InstCombine/InstCombineAtomicRMW.cpp
@@ -57,15 +57,23 @@ bool isIdempotentRMW(AtomicRMWInst& RMWI) {
 }
 
 /// Return true if the given instruction always produces a value in memory
-/// equivelent to its value operand.
+/// equivalent to its value operand.
 bool isSaturating(AtomicRMWInst& RMWI) {
+  if (auto CF = dyn_cast<ConstantFP>(RMWI.getValOperand()))
+    switch(RMWI.getOperation()) {
+    case AtomicRMWInst::FAdd:
+    case AtomicRMWInst::FSub:
+      return CF->isNaN();
+    default:
+      return false;
+    };
+
   auto C = dyn_cast<ConstantInt>(RMWI.getValOperand());
   if(!C)
     return false;
 
   switch(RMWI.getOperation()) {
   default:
-    // TODO: fadd, fsub w/Nan
     return false;
   case AtomicRMWInst::Xchg:
     return true;

diff --git a/test/Transforms/InstCombine/atomicrmw.ll b/test/Transforms/InstCombine/atomicrmw.ll
index e43d4a02c2b2c1b036c66aae880f9d60e645b29e..6b594bed33c65558d775acd01305962e970ac305 100644 (file)
--- a/test/Transforms/InstCombine/atomicrmw.ll
+++ b/test/Transforms/InstCombine/atomicrmw.ll
@@ -214,7 +214,7 @@ define i8 @sat_max_smax_char(i8* %addr) {
 }
 
 ; CHECK-LABEL: sat_fadd_nan
-; CHECK-NEXT: %res = atomicrmw fadd double* %addr, double 0x7FF00000FFFFFFFF release
+; CHECK-NEXT: %res = atomicrmw xchg double* %addr, double 0x7FF00000FFFFFFFF release
 ; CHECK-NEXT: ret double %res
 define double @sat_fadd_nan(double* %addr) {
   %res = atomicrmw fadd double* %addr, double 0x7FF00000FFFFFFFF release
@@ -222,7 +222,7 @@ define double @sat_fadd_nan(double* %addr) {
 }
 
 ; CHECK-LABEL: sat_fsub_nan
-; CHECK-NEXT: %res = atomicrmw fsub double* %addr, double 0x7FF00000FFFFFFFF release
+; CHECK-NEXT: %res = atomicrmw xchg double* %addr, double 0x7FF00000FFFFFFFF release
 ; CHECK-NEXT: ret double %res
 define double @sat_fsub_nan(double* %addr) {
   %res = atomicrmw fsub double* %addr, double 0x7FF00000FFFFFFFF release
@@ -230,7 +230,7 @@ define double @sat_fsub_nan(double* %addr) {
 }
 
 ; CHECK-LABEL: sat_fsub_nan_unused
-; CHECK-NEXT: atomicrmw fsub double* %addr, double 0x7FF00000FFFFFFFF monotonic
+; CHECK-NEXT: store atomic double 0x7FF00000FFFFFFFF, double* %addr monotonic, align 8
 ; CHECK-NEXT: ret void
 define void @sat_fsub_nan_unused(double* %addr) {
   atomicrmw fsub double* %addr, double 0x7FF00000FFFFFFFF monotonic