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Make CodePlacementOpt detect special EH control flow by

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checking whether AnalyzeBranch disagrees with the CFG
directly, rather than looking for EH_LABEL instructions.
EH_LABEL instructions aren't always at the end of the
block, due to FP_REG_KILL and other things. This fixes
an infinite loop compiling MultiSource/Benchmarks/Bullet.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@96611 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman 2010-02-18 21:25:53 +00:00
parent 0ce7b1255c
commit 49d7f8d341
2 changed files with 53 additions and 7 deletions
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15
lib/CodeGen/CodePlacementOpt.cpp
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@ -102,13 +102,6 @@ bool CodePlacementOpt::HasAnalyzableTerminator(MachineBasicBlock *MBB) {
// Conservatively ignore EH landing pads.
if (MBB->isLandingPad()) return false;
// Ignore blocks which look like they might have EH-related control flow.
// At the time of this writing, there are blocks which AnalyzeBranch
// thinks end in single uncoditional branches, yet which have two CFG
// successors. Code in this file is not prepared to reason about such things.
if (!MBB->empty() && MBB->back().isEHLabel())
return false;
// Aggressively handle return blocks and similar constructs.
if (MBB->succ_empty()) return true;
@ -118,6 +111,14 @@ bool CodePlacementOpt::HasAnalyzableTerminator(MachineBasicBlock *MBB) {
// Make sure the terminator is understood.
if (TII->AnalyzeBranch(*MBB, TBB, FBB, Cond))
return false;
// Ignore blocks which look like they might have EH-related control flow.
// AnalyzeBranch thinks it knows how to analyze such things, but it doesn't
// recognize the possibility of a control transfer through an unwind.
// Such blocks contain EH_LABEL instructions, however they may be in the
// middle of the block. Instead of searching for them, just check to see
// if the CFG disagrees with AnalyzeBranch.
if (1u + !Cond.empty() != MBB->succ_size())
return false;
// Make sure we have the option of reversing the condition.
if (!Cond.empty() && TII->ReverseBranchCondition(Cond))
return false;

45
test/CodeGen/X86/code_placement_eh.ll Normal file
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@ -0,0 +1,45 @@
; RUN: llc < %s
; CodePlacementOpt shouldn't try to modify this loop because
; it involves EH edges.
target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128-n8:16:32"
target triple = "i386-apple-darwin10.0"
define void @foo() {
invcont5:
br label %bb15
.noexc3: ; preds = %bb15
br i1 undef, label %bb18.i5.i, label %bb15
.noexc6.i.i: ; preds = %bb18.i5.i
%tmp2021 = invoke float @cosf(float 0.000000e+00) readonly
to label %bb18.i5.i unwind label %lpad.i.i ; <float> [#uses=0]
bb18.i5.i: ; preds = %.noexc6.i.i, %bb51.i
%tmp2019 = invoke float @sinf(float 0.000000e+00) readonly
to label %.noexc6.i.i unwind label %lpad.i.i ; <float> [#uses=0]
lpad.i.i: ; preds = %bb18.i5.i, %.noexc6.i.i
%eh_ptr.i.i = call i8* @llvm.eh.exception() ; <i8*> [#uses=1]
unreachable
lpad59.i: ; preds = %bb15
%eh_ptr60.i = call i8* @llvm.eh.exception() ; <i8*> [#uses=1]
unreachable
bb15: ; preds = %.noexc3, %invcont5
invoke fastcc void @_ZN28btHashedOverlappingPairCacheC2Ev()
to label %.noexc3 unwind label %lpad59.i
}
declare i8* @llvm.eh.exception() nounwind readonly
declare i32 @llvm.eh.selector(i8*, i8*, ...) nounwind
declare float @sinf(float) readonly
declare float @cosf(float) readonly
declare fastcc void @_ZN28btHashedOverlappingPairCacheC2Ev() align 2