From 2efbbb38ba7b9601202f2271301f07195dea8959 Mon Sep 17 00:00:00 2001
From: Chris Lattner <sabre@nondot.org>
Date: Wed, 26 Nov 2008 00:26:16 +0000
Subject: Teach CodeGenPrepare to look through Bitcast instructions when
 attempting to optimize addressing modes.  This allows us to optimize things
 like isel-sink2.ll into:

	movl	4(%esp), %eax
	cmpb	$0, 4(%eax)
	jne	LBB1_2	## F
LBB1_1:	## TB
	movl	$4, %eax
	ret
LBB1_2:	## F
	movzbl	7(%eax), %eax
	ret

instead of:

_test:
	movl	4(%esp), %eax
	cmpb	$0, 4(%eax)
	leal	4(%eax), %eax
	jne	LBB1_2	## F
LBB1_1:	## TB
	movl	$4, %eax
	ret
LBB1_2:	## F
	movzbl	3(%eax), %eax
	ret

This shrinks (e.g.) 403.gcc from 1133510 to 1128345 lines of .s.

Note that the 2008-10-16-SpillerBug.ll testcase is dubious at best, I doubt
it is really testing what it thinks it is.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60068 91177308-0d34-0410-b5e6-96231b3b80d8
---
 test/CodeGen/X86/isel-sink2.ll | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)
 create mode 100644 test/CodeGen/X86/isel-sink2.ll

(limited to 'test/CodeGen/X86/isel-sink2.ll')

diff --git a/test/CodeGen/X86/isel-sink2.ll b/test/CodeGen/X86/isel-sink2.ll
new file mode 100644
index 0000000..d8e27e9
--- /dev/null
+++ b/test/CodeGen/X86/isel-sink2.ll
@@ -0,0 +1,16 @@
+; RUN: llvm-as < %s | llc -march=x86 | grep {movzbl.7(%...)}
+; RUN: llvm-as < %s | llc -march=x86 | not grep leal
+
+define i8 @test(i32 *%P) nounwind {
+  %Q = getelementptr i32* %P, i32 1
+  %R = bitcast i32* %Q to i8*
+  %S = load i8* %R
+  %T = icmp eq i8 %S, 0
+  br i1 %T, label %TB, label %F
+TB:
+  ret i8 4
+F:
+  %U = getelementptr i8* %R, i32 3
+  %V = load i8* %U
+  ret i8 %V
+}
-- 
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