Find loop back edges only after empty blocks are eliminated.

Evan Cheng · Evan Cheng · commit 8804293fe977 · 2009-01-05T21:17:27.000Z
llvm-svn: 61752
diff --git a/llvm/lib/Transforms/Scalar/CodeGenPrepare.cpp b/llvm/lib/Transforms/Scalar/CodeGenPrepare.cpp
@@ -125,12 +125,13 @@ void CodeGenPrepare::findLoopBackEdges(Function &F) {
 bool CodeGenPrepare::runOnFunction(Function &F) {
   bool EverMadeChange = false;
 
-  findLoopBackEdges(F);
-
   // First pass, eliminate blocks that contain only PHI nodes and an
   // unconditional branch.
   EverMadeChange |= EliminateMostlyEmptyBlocks(F);
 
+  // Now find loop back edges.
+  findLoopBackEdges(F);
+
   bool MadeChange = true;
   while (MadeChange) {
     MadeChange = false;
diff --git a/llvm/test/CodeGen/X86/remat-mov0.ll b/llvm/test/CodeGen/X86/remat-mov0.ll
@@ -1,4 +1,4 @@
-; RUN: llvm-as < %s | llc -march=x86 | grep xor | count 1
+; RUN: llvm-as < %s | llc -march=x86 | grep xor | count 2
 
 	%struct.FILE = type { i8*, i32, i32, i16, i16, %struct.__sbuf, i32, i8*, i32 (i8*)*, i32 (i8*, i8*, i32)*, i64 (i8*, i64, i32)*, i32 (i8*, i8*, i32)*, %struct.__sbuf, %struct.__sFILEX*, i32, [3 x i8], [1 x i8], %struct.__sbuf, i32, i64 }
 	%struct.ImgT = type { i8, i8*, i8*, %struct.FILE*, i32, i32, i32, i32, i8*, double*, float*, float*, float*, i32*, double, double, i32*, double*, i32*, i32* }

Original file line number	Diff line number	Diff line change
`@@ -1,4 +1,4 @@`
`1`		`-; RUN: llvm-as < %s \| llc -march=x86 \| grep xor \| count 1`
	`1`	`+; RUN: llvm-as < %s \| llc -march=x86 \| grep xor \| count 2`
`2`	`2`
`3`	`3`	`%struct.FILE = type { i8, i32, i32, i16, i16, %struct.__sbuf, i32, i8, i32 (i8), i32 (i8, i8, i32), i64 (i8, i64, i32), i32 (i8, i8, i32), %struct.__sbuf, %struct.__sFILEX*, i32, [3 x i8], [1 x i8], %struct.__sbuf, i32, i64 }`
`4`	`4`	`%struct.ImgT = type { i8, i8, i8, %struct.FILE, i32, i32, i32, i32, i8, double, float, float, float, i32, double, double, i32, double, i32, i32* }`