Add llvm patch corresponding to r288195.

2015-09-25 18:21:48 +00:00 · 2015-09-25 18:21:48 +00:00 · ba96f361ba
commit ba96f361ba
parent 98e67009c0
1 changed files with 83 additions and 0 deletions
--- a/contrib/llvm/patches/patch-06-llvm-r248439-fdiv-hoisting.diff
+++ b/contrib/llvm/patches/patch-06-llvm-r248439-fdiv-hoisting.diff
@ -0,0 +1,83 @@
+Pull in r248439 from upstream llvm trunk (by Sanjay Patel):
+
+  set div/rem default values to 'expensive' in TargetTransformInfo's
+  cost model
+
+  ...because that's what the cost model was intended to do.
+
+  As discussed in D12882, this fix has a temporary unintended
+  consequence for SimplifyCFG: it causes us to not speculate an fdiv.
+  However, two wrongs make PR24818 right, and two wrongs make PR24343
+  act right even though it's really still wrong.
+
+  I intend to correct SimplifyCFG and add to CodeGenPrepare to account
+  for this cost model change and preserve the righteousness for the bug
+  report cases.
+
+  https://llvm.org/bugs/show_bug.cgi?id=24818
+  https://llvm.org/bugs/show_bug.cgi?id=24343
+
+  Differential Revision: http://reviews.llvm.org/D12882
+
+This fixes the too-eager fdiv hoisting in pow(), which could lead to
+unexpected floating point exceptions.
+
+Introduced here: http://svnweb.freebsd.org/changeset/base/288195
+
+Index: include/llvm/Analysis/TargetTransformInfoImpl.h
+===================================================================
+--- include/llvm/Analysis/TargetTransformInfoImpl.h
+++ include/llvm/Analysis/TargetTransformInfoImpl.h
+@@ -60,6 +60,14 @@ class TargetTransformInfoImplBase {
+       // Otherwise, the default basic cost is used.
+       return TTI::TCC_Basic;
+ 
+    case Instruction::FDiv:
+    case Instruction::FRem:
+    case Instruction::SDiv:
+    case Instruction::SRem:
+    case Instruction::UDiv:
+    case Instruction::URem:
+      return TTI::TCC_Expensive;
+
+     case Instruction::IntToPtr: {
+       // An inttoptr cast is free so long as the input is a legal integer type
+       // which doesn't contain values outside the range of a pointer.
+Index: test/Transforms/SimplifyCFG/speculate-math.ll
+===================================================================
+--- test/Transforms/SimplifyCFG/speculate-math.ll
+++ test/Transforms/SimplifyCFG/speculate-math.ll
+@@ -7,6 +7,33 @@ declare float @llvm.fabs.f32(float) nounwind reado
+ declare float @llvm.minnum.f32(float, float) nounwind readonly
+ declare float @llvm.maxnum.f32(float, float) nounwind readonly
+ 
+; FIXME: This is intended to be a temporary test. As discussed in 
+; D12882, we actually do want to speculate even expensive operations
+; in SimplifyCFG because it can expose more optimizations for other
+; passes. Therefore, we either need to adjust SimplifyCFG's 
+; calculations that use the TTI cost model or use a different cost
+; model for deciding which ops should be speculated in SimplifyCFG. 
+; We should also be using the TTI cost model later - for example in
+; CodeGenPrepare - to potentially undo this speculation.
+
+; Do not speculate fdiv by default because it is generally expensive. 
+
+; CHECK-LABEL: @fdiv_test(
+; CHECK-NOT: select
+define double @fdiv_test(double %a, double %b) {
+entry:
+  %cmp = fcmp ogt double %a, 0.0
+  br i1 %cmp, label %cond.true, label %cond.end
+
+cond.true:
+  %div = fdiv double %b, %a
+  br label %cond.end
+
+cond.end:
+  %cond = phi double [ %div, %cond.true ], [ 0.0, %entry ]
+  ret double %cond
+}
+
+ ; CHECK-LABEL: @sqrt_test(
+ ; CHECK: select
+ define void @sqrt_test(float addrspace(1)* noalias nocapture %out, float %a) nounwind {