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don't eliminate load from volatile value on paths where the load is dead.
This fixes the second half of PR2262 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@50430 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -9396,6 +9396,15 @@ Instruction *InstCombiner::FoldPHIArgOpIntoPHI(PHINode &PN) {
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LI->getParent() != PN.getIncomingBlock(i) ||
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!isSafeToSinkLoad(LI))
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return 0;
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// If the PHI is volatile and its block has multiple successors, sinking
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// it would remove a load of the volatile value from the path through the
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// other successor.
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if (isVolatile &&
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LI->getParent()->getTerminator()->getNumSuccessors() != 1)
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return 0;
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} else if (I->getOperand(1) != ConstantOp) {
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return 0;
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}
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@ -0,0 +1,25 @@
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; RUN: llvm-as < %s | opt -instcombine | llvm-dis | grep {volatile load} | count 2
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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"
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target triple = "i386-apple-darwin8"
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@g_1 = internal global i32 0 ; <i32*> [#uses=3]
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define i32 @main() nounwind {
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entry:
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%tmp93 = icmp slt i32 0, 10 ; <i1> [#uses=0]
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%tmp34 = volatile load i32* @g_1, align 4 ; <i32> [#uses=1]
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br label %bb
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bb: ; preds = %bb, %entry
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%b.0.reg2mem.0 = phi i32 [ 0, %entry ], [ %tmp6, %bb ] ; <i32> [#uses=1]
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%tmp3.reg2mem.0 = phi i32 [ %tmp34, %entry ], [ %tmp3, %bb ] ; <i32> [#uses=1]
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%tmp4 = add i32 %tmp3.reg2mem.0, 5 ; <i32> [#uses=1]
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volatile store i32 %tmp4, i32* @g_1, align 4
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%tmp6 = add i32 %b.0.reg2mem.0, 1 ; <i32> [#uses=2]
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%tmp9 = icmp slt i32 %tmp6, 10 ; <i1> [#uses=1]
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%tmp3 = volatile load i32* @g_1, align 4 ; <i32> [#uses=1]
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br i1 %tmp9, label %bb, label %bb11
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bb11: ; preds = %bb
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ret i32 0
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}
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