[llvm-commits] CVS: llvm/lib/Target/X86/README.txt

[Evan Cheng]

Changes in directory llvm/lib/Target/X86:

README.txt updated: 1.90 -> 1.91
---
Log message:

Another entry

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Diffs of the changes:  (+35 -0)

 README.txt |   35 +++++++++++++++++++++++++++++++++++
 1 files changed, 35 insertions(+)


Index: llvm/lib/Target/X86/README.txt
diff -u llvm/lib/Target/X86/README.txt:1.90 llvm/lib/Target/X86/README.txt:1.91
--- llvm/lib/Target/X86/README.txt:1.90	Mon Apr 17 19:21:01 2006
+++ llvm/lib/Target/X86/README.txt	Mon Apr 17 20:22:57 2006
@@ -961,3 +961,38 @@
 to three-address transformation.
 
 It also exposes some other problems. See MOV32ri -3 and the spills.
+
+//===---------------------------------------------------------------------===//
+
+http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25500
+
+LLVM is producing bad code.
+
+LBB_main_4:	# cond_true44
+	addps %xmm1, %xmm2
+	subps %xmm3, %xmm2
+	movaps (%ecx), %xmm4
+	movaps %xmm2, %xmm1
+	addps %xmm4, %xmm1
+	addl $16, %ecx
+	incl %edx
+	cmpl $262144, %edx
+	movaps %xmm3, %xmm2
+	movaps %xmm4, %xmm3
+	jne LBB_main_4	# cond_true44
+
+There are two problems. 1) No need to two loop induction variables. We can
+compare against 262144 * 16. 2) Poor register allocation decisions. We should
+be able eliminate one of the movaps:
+
+	addps %xmm1, %xmm2
+	subps %xmm3, %xmm2
+	movaps (%ecx), %xmm4
+	movaps %xmm2, %xmm2   <=== Eliminate!
+	addps %xmm4, %xmm2
+	addl $16, %ecx
+	incl %edx
+	cmpl $262144, %edx
+	movaps %xmm3, %xmm1
+	movaps %xmm4, %xmm3
+	jne LBB_main_4	# cond_true44