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When checking whether the special handling for an addrec increment which

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doesn't dominate the header is needed, don't check whether the increment
expression has computable loop evolution. While the operands of an
addrec are required to be loop-invariant, they're not required to 
dominate any part of the loop. This fixes PR6914.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@102389 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman 2010-04-26 21:46:36 +00:00
parent 585c40129f
commit 948c8a3e3d
3 changed files with 26 additions and 4 deletions
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2
lib/Analysis/README.txt
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@ -17,7 +17,7 @@ which is very inefficient when expanded into code.
//===---------------------------------------------------------------------===//
In test/CodeGen/X86/lsr-delayed-fold.ll,
In formatValue in test/CodeGen/X86/lsr-delayed-fold.ll,
ScalarEvolution is forming this expression:

3
lib/Analysis/ScalarEvolutionExpander.cpp
View File

@ -995,8 +995,7 @@ Value *SCEVExpander::expandAddRecExprLiterally(const SCEVAddRecExpr *S) {
// Strip off any non-loop-dominating component from the addrec step.
const SCEV *Step = Normalized->getStepRecurrence(SE);
const SCEV *PostLoopScale = 0;
if (!Step->hasComputableLoopEvolution(L) &&
!Step->dominates(L->getHeader(), SE.DT)) {
if (!Step->dominates(L->getHeader(), SE.DT)) {
PostLoopScale = Step;
Step = SE.getIntegerSCEV(1, Normalized->getType());
Normalized =

25
test/CodeGen/X86/lsr-delayed-fold.ll
View File

@ -1,8 +1,8 @@
; RUN: llc -march=x86-64 < %s > /dev/null
; rdar://7886751
; ScalarEvolution misses an opportunity to fold ((trunc x) + (trunc -x) + y),
; but LSR should tolerate this.
; rdar://7886751
target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64"
target triple = "x86_64-apple-darwin11.0"
@ -26,3 +26,26 @@ bb15: ; preds = %bb21, %bb12
bb24: ; preds = %bb21, %bb11
unreachable
}
; ScalarEvolution should be able to correctly expand the crazy addrec here.
; PR6914
define void @int323() nounwind {
entry:
br label %for.cond
for.cond: ; preds = %lbl_264, %for.inc, %entry
%g_263.tmp.1 = phi i8 [ undef, %entry ], [ %g_263.tmp.1, %for.cond ]
%p_95.addr.0 = phi i8 [ 0, %entry ], [ %add, %for.cond ]
%add = add i8 %p_95.addr.0, 1 ; <i8> [#uses=1]
br i1 undef, label %for.cond, label %lbl_264
lbl_264: ; preds = %if.end, %lbl_264.preheader
%g_263.tmp.0 = phi i8 [ %g_263.tmp.1, %for.cond ] ; <i8> [#uses=1]
%tmp7 = load i16* undef ; <i16> [#uses=1]
%conv8 = trunc i16 %tmp7 to i8 ; <i8> [#uses=1]
%mul.i = mul i8 %p_95.addr.0, %p_95.addr.0 ; <i8> [#uses=1]
%mul.i18 = mul i8 %mul.i, %conv8 ; <i8> [#uses=1]
%tobool12 = icmp eq i8 %mul.i18, 0 ; <i1> [#uses=1]
unreachable
}