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https://github.com/RPCS3/llvm-mirror.git
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a67cf70e74
Summary: Make isGuaranteedToExecute use the isGuaranteedToTransferExecutionToSuccessor helper, and make that helper a bit more accurate. There's a potential performance impact here from assuming that arbitrary calls might not return. This probably has little impact on loads and stores to a pointer because most things alias analysis can reason about are dereferenceable anyway. The other impacts, like less aggressive hoisting of sdiv by a variable and less aggressive hoisting around volatile memory operations, are unlikely to matter for real code. This also impacts SCEV, which uses the same helper. It's a minor improvement there because we can tell that, for example, memcpy always returns normally. Strictly speaking, it's also introducing a bug, but it's not any worse than everywhere else we assume readonly functions terminate. Fixes http://llvm.org/PR27857. Reviewers: hfinkel, reames, chandlerc, sanjoy Subscribers: broune, llvm-commits Differential Revision: http://reviews.llvm.org/D21167 llvm-svn: 272489
124 lines
3.1 KiB
LLVM
124 lines
3.1 KiB
LLVM
; RUN: opt < %s -licm -S | FileCheck %s
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@X = global i32 0 ; <i32*> [#uses=1]
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declare void @foo()
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; This testcase tests for a problem where LICM hoists
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; potentially trapping instructions when they are not guaranteed to execute.
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define i32 @test1(i1 %c) {
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; CHECK-LABEL: @test1(
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%A = load i32, i32* @X ; <i32> [#uses=2]
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br label %Loop
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Loop: ; preds = %LoopTail, %0
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call void @foo( )
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br i1 %c, label %LoopTail, label %IfUnEqual
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IfUnEqual: ; preds = %Loop
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; CHECK: IfUnEqual:
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; CHECK-NEXT: sdiv i32 4, %A
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%B1 = sdiv i32 4, %A ; <i32> [#uses=1]
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br label %LoopTail
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LoopTail: ; preds = %IfUnEqual, %Loop
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%B = phi i32 [ 0, %Loop ], [ %B1, %IfUnEqual ] ; <i32> [#uses=1]
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br i1 %c, label %Loop, label %Out
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Out: ; preds = %LoopTail
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%C = sub i32 %A, %B ; <i32> [#uses=1]
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ret i32 %C
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}
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declare void @foo2(i32) nounwind
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;; It is ok and desirable to hoist this potentially trapping instruction.
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define i32 @test2(i1 %c) {
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; CHECK-LABEL: @test2(
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; CHECK-NEXT: load i32, i32* @X
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; CHECK-NEXT: %B = sdiv i32 4, %A
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%A = load i32, i32* @X
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br label %Loop
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Loop:
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;; Should have hoisted this div!
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%B = sdiv i32 4, %A
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br label %loop2
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loop2:
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call void @foo2( i32 %B )
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br i1 %c, label %Loop, label %Out
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Out:
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%C = sub i32 %A, %B
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ret i32 %C
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}
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; This loop invariant instruction should be constant folded, not hoisted.
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define i32 @test3(i1 %c) {
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; CHECK-LABEL: define i32 @test3(
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; CHECK: call void @foo2(i32 6)
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%A = load i32, i32* @X ; <i32> [#uses=2]
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br label %Loop
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Loop:
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%B = add i32 4, 2 ; <i32> [#uses=2]
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call void @foo2( i32 %B )
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br i1 %c, label %Loop, label %Out
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Out: ; preds = %Loop
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%C = sub i32 %A, %B ; <i32> [#uses=1]
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ret i32 %C
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}
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; CHECK-LABEL: @test4(
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; CHECK: call
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; CHECK: sdiv
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; CHECK: ret
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define i32 @test4(i32 %x, i32 %y) nounwind uwtable ssp {
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entry:
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br label %for.body
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for.body: ; preds = %entry, %for.body
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%i.02 = phi i32 [ 0, %entry ], [ %inc, %for.body ]
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%n.01 = phi i32 [ 0, %entry ], [ %add, %for.body ]
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call void @foo_may_call_exit(i32 0)
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%div = sdiv i32 %x, %y
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%add = add nsw i32 %n.01, %div
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%inc = add nsw i32 %i.02, 1
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%cmp = icmp slt i32 %inc, 10000
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br i1 %cmp, label %for.body, label %for.end
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for.end: ; preds = %for.body
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%n.0.lcssa = phi i32 [ %add, %for.body ]
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ret i32 %n.0.lcssa
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}
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declare void @foo_may_call_exit(i32)
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; PR14854
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; CHECK-LABEL: @test5(
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; CHECK: extractvalue
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; CHECK: br label %tailrecurse
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; CHECK: tailrecurse:
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; CHECK: ifend:
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; CHECK: insertvalue
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define { i32*, i32 } @test5(i32 %i, { i32*, i32 } %e) {
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entry:
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br label %tailrecurse
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tailrecurse: ; preds = %then, %entry
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%i.tr = phi i32 [ %i, %entry ], [ %cmp2, %then ]
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%out = extractvalue { i32*, i32 } %e, 1
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%d = insertvalue { i32*, i32 } %e, i32* null, 0
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%cmp1 = icmp sgt i32 %out, %i.tr
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br i1 %cmp1, label %then, label %ifend
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then: ; preds = %tailrecurse
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call void @foo()
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%cmp2 = add i32 %i.tr, 1
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br label %tailrecurse
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ifend: ; preds = %tailrecurse
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ret { i32*, i32 } %d
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}
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