[PATCH] D18744: [CodeGenPrepare] Avoid sinking soft-FP comparisons

[whitequark via llvm-commits]

This revision was automatically updated to reflect the committed changes.
Closed by commit rL265264: [CodeGenPrepare] Avoid sinking soft-FP comparisons (authored by whitequark).

Changed prior to commit:
  http://reviews.llvm.org/D18744?vs=52503&id=52505#toc

Repository:
  rL LLVM

http://reviews.llvm.org/D18744

Files:
  llvm/trunk/lib/CodeGen/CodeGenPrepare.cpp
  llvm/trunk/test/Transforms/CodeGenPrepare/X86/fcmp-sinking.ll

Index: llvm/trunk/test/Transforms/CodeGenPrepare/X86/fcmp-sinking.ll
===================================================================
--- llvm/trunk/test/Transforms/CodeGenPrepare/X86/fcmp-sinking.ll
+++ llvm/trunk/test/Transforms/CodeGenPrepare/X86/fcmp-sinking.ll
@@ -0,0 +1,29 @@
+; RUN: opt %s -codegenprepare -mattr=+soft-float -S | FileCheck %s -check-prefix=CHECK -check-prefix=SOFTFP
+; RUN: opt %s -codegenprepare -mattr=-soft-float -S | FileCheck %s -check-prefix=CHECK -check-prefix=HARDFP
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+; CHECK-LABEL: @foo
+; CHECK:       entry:
+; SOFTFP:      fcmp
+; HARDFP-NOT:  fcmp
+; CHECK:       body:
+; SOFTFP-NOT:  fcmp
+; HARDFP:      fcmp
+define void @foo(float %a, float %b) {
+entry:
+  %c = fcmp oeq float %a, %b
+  br label %head
+head:
+  %IND = phi i32 [ 0, %entry ], [ %IND.new, %body1 ]
+  %CMP = icmp slt i32 %IND, 1250
+  br i1 %CMP, label %body, label %tail
+body:
+  br i1 %c, label %body1, label %tail
+body1:
+  %IND.new = add i32 %IND, 1
+  br label %head
+tail:
+  ret void
+}
Index: llvm/trunk/lib/CodeGen/CodeGenPrepare.cpp
===================================================================
--- llvm/trunk/lib/CodeGen/CodeGenPrepare.cpp
+++ llvm/trunk/lib/CodeGen/CodeGenPrepare.cpp
@@ -855,10 +855,14 @@
 /// lose; some adjustment may be wanted there.
 ///
 /// Return true if any changes are made.
-static bool SinkCmpExpression(CmpInst *CI) {
+static bool SinkCmpExpression(CmpInst *CI, const TargetLowering &TLI) {
   BasicBlock *DefBB = CI->getParent();
 
-  /// Only insert a cmp in each block once.
+  // Avoid sinking soft-FP comparisons, since this can move them into a loop.
+  if (TLI.useSoftFloat() && isa<FCmpInst>(CI))
+    return false;
+
+  // Only insert a cmp in each block once.
   DenseMap<BasicBlock*, CmpInst*> InsertedCmps;
 
   bool MadeChange = false;
@@ -906,8 +910,8 @@
   return MadeChange;
 }
 
-static bool OptimizeCmpExpression(CmpInst *CI) {
-  if (SinkCmpExpression(CI))
+static bool OptimizeCmpExpression(CmpInst *CI, const TargetLowering &TLI) {
+  if (SinkCmpExpression(CI, TLI))
     return true;
 
   if (CombineUAddWithOverflow(CI))
@@ -5173,7 +5177,7 @@
 
   if (CmpInst *CI = dyn_cast<CmpInst>(I))
     if (!TLI || !TLI->hasMultipleConditionRegisters())
-      return OptimizeCmpExpression(CI);
+      return OptimizeCmpExpression(CI, *TLI);
 
   if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
     stripInvariantGroupMetadata(*LI);


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