[llvm-commits] [llvm] r122217 - in /llvm/trunk: lib/Target/X86/X86InstrCompiler.td test/CodeGen/X86/add.ll

[Chris Lattner]

Author: lattner
Date: Sun Dec 19 19:16:03 2010
New Revision: 122217

URL: http://llvm.org/viewvc/llvm-project?rev=122217&view=rev
Log:
We lower setb to sbb with the hope that the and will go away, when it 
doesn't, match it back to setb.

On a 64-bit version of the testcase before we'd get:

	movq	%rdi, %rax
	addq	%rsi, %rax
	sbbb	%dl, %dl
	andb	$1, %dl
	ret

now we get:

	movq	%rdi, %rax
	addq	%rsi, %rax
	setb	%dl
	ret



Modified:
    llvm/trunk/lib/Target/X86/X86InstrCompiler.td
    llvm/trunk/test/CodeGen/X86/add.ll

Modified: llvm/trunk/lib/Target/X86/X86InstrCompiler.td
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86InstrCompiler.td?rev=122217&r1=122216&r2=122217&view=diff
==============================================================================
--- llvm/trunk/lib/Target/X86/X86InstrCompiler.td (original)
+++ llvm/trunk/lib/Target/X86/X86InstrCompiler.td Sun Dec 19 19:16:03 2010
@@ -207,6 +207,12 @@
 def : Pat<(i64 (sext (i8 (X86setcc_c X86_COND_B, EFLAGS)))),
           (SETB_C64r)>;
 
+// We canonicalize 'setb' to "(and (sbb reg,reg), 1)" on the hope that the and
+// will be eliminated and that the sbb can be extended up to a wider type.  When
+// this happens, it is great.  However, if we are left with an 8-bit sbb and an
+// and, we might as well just match it as a setb.
+def : Pat<(and (i8 (X86setcc_c X86_COND_B, EFLAGS)), 1),
+          (SETBr)>;
 
 //===----------------------------------------------------------------------===//
 // String Pseudo Instructions

Modified: llvm/trunk/test/CodeGen/X86/add.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/add.ll?rev=122217&r1=122216&r2=122217&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/X86/add.ll (original)
+++ llvm/trunk/test/CodeGen/X86/add.ll Sun Dec 19 19:16:03 2010
@@ -92,3 +92,12 @@
 ; X64:	ret
 }
 
+define {i32, i1} @test7(i32 %v1, i32 %v2) nounwind {
+   %t = call {i32, i1} @llvm.uadd.with.overflow.i32(i32 %v1, i32 %v2)
+   ret {i32, i1} %t
+}
+
+; X64: test7:
+; X64: addl %esi, %eax
+; X64-NEXT: setb %dl
+; X64-NEXT: ret