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add a note from PR5313
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86146 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -1229,6 +1229,40 @@ GCC PR33344 is a similar case.
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//===---------------------------------------------------------------------===//
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[PHI TRANSLATE INDEXED GEPs] PR5313
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Load redundancy elimination for simple loop. This loop:
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void append_text(const char* text,unsigned char * const io) {
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while(*text)
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*io=*text++;
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}
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Compiles to have a fully redundant load in the loop (%2):
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define void @append_text(i8* nocapture %text, i8* nocapture %io) nounwind {
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entry:
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%0 = load i8* %text, align 1 ; <i8> [#uses=1]
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%1 = icmp eq i8 %0, 0 ; <i1> [#uses=1]
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br i1 %1, label %return, label %bb
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bb: ; preds = %bb, %entry
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%indvar = phi i32 [ 0, %entry ], [ %tmp, %bb ] ; <i32> [#uses=2]
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%text_addr.04 = getelementptr i8* %text, i32 %indvar ; <i8*> [#uses=1]
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%2 = load i8* %text_addr.04, align 1 ; <i8> [#uses=1]
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store i8 %2, i8* %io, align 1
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%tmp = add i32 %indvar, 1 ; <i32> [#uses=2]
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%scevgep = getelementptr i8* %text, i32 %tmp ; <i8*> [#uses=1]
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%3 = load i8* %scevgep, align 1 ; <i8> [#uses=1]
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%4 = icmp eq i8 %3, 0 ; <i1> [#uses=1]
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br i1 %4, label %return, label %bb
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return: ; preds = %bb, %entry
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ret void
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}
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//===---------------------------------------------------------------------===//
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There are many load PRE testcases in testsuite/gcc.dg/tree-ssa/loadpre* in the
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GCC testsuite. There are many pre testcases as ssa-pre-*.c
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