[llvm-commits] [llvm] r86146 - /llvm/trunk/lib/Target/README.txt
Chris Lattner
sabre at nondot.org
Thu Nov 5 10:19:19 PST 2009
Author: lattner
Date: Thu Nov 5 12:19:19 2009
New Revision: 86146
URL: http://llvm.org/viewvc/llvm-project?rev=86146&view=rev
Log:
add a note from PR5313
Modified:
llvm/trunk/lib/Target/README.txt
Modified: llvm/trunk/lib/Target/README.txt
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/README.txt?rev=86146&r1=86145&r2=86146&view=diff
==============================================================================
--- llvm/trunk/lib/Target/README.txt (original)
+++ llvm/trunk/lib/Target/README.txt Thu Nov 5 12:19:19 2009
@@ -1229,6 +1229,40 @@
//===---------------------------------------------------------------------===//
+[PHI TRANSLATE INDEXED GEPs] PR5313
+
+Load redundancy elimination for simple loop. This loop:
+
+void append_text(const char* text,unsigned char * const io) {
+ while(*text)
+ *io=*text++;
+}
+
+Compiles to have a fully redundant load in the loop (%2):
+
+define void @append_text(i8* nocapture %text, i8* nocapture %io) nounwind {
+entry:
+ %0 = load i8* %text, align 1 ; <i8> [#uses=1]
+ %1 = icmp eq i8 %0, 0 ; <i1> [#uses=1]
+ br i1 %1, label %return, label %bb
+
+bb: ; preds = %bb, %entry
+ %indvar = phi i32 [ 0, %entry ], [ %tmp, %bb ] ; <i32> [#uses=2]
+ %text_addr.04 = getelementptr i8* %text, i32 %indvar ; <i8*> [#uses=1]
+ %2 = load i8* %text_addr.04, align 1 ; <i8> [#uses=1]
+ store i8 %2, i8* %io, align 1
+ %tmp = add i32 %indvar, 1 ; <i32> [#uses=2]
+ %scevgep = getelementptr i8* %text, i32 %tmp ; <i8*> [#uses=1]
+ %3 = load i8* %scevgep, align 1 ; <i8> [#uses=1]
+ %4 = icmp eq i8 %3, 0 ; <i1> [#uses=1]
+ br i1 %4, label %return, label %bb
+
+return: ; preds = %bb, %entry
+ ret void
+}
+
+//===---------------------------------------------------------------------===//
+
There are many load PRE testcases in testsuite/gcc.dg/tree-ssa/loadpre* in the
GCC testsuite. There are many pre testcases as ssa-pre-*.c
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