X86: Lower a select directly to a setcc_carry if possible.

  int test(unsigned long a, unsigned long b) { return -(a < b); }
compiles to
  _test:                              ## @test
    cmpq  %rsi, %rdi                  ## encoding: [0x48,0x39,0xf7]
    sbbl  %eax, %eax                  ## encoding: [0x19,0xc0]
    ret                               ## encoding: [0xc3]
instead of
  _test:                              ## @test
    xorl  %ecx, %ecx                  ## encoding: [0x31,0xc9]
    cmpq  %rsi, %rdi                  ## encoding: [0x48,0x39,0xf7]
    movl  $-1, %eax                   ## encoding: [0xb8,0xff,0xff,0xff,0xff]
    cmovael %ecx, %eax                ## encoding: [0x0f,0x43,0xc1]
    ret                               ## encoding: [0xc3]

llvm-svn: 122451

1 files changed, 19 insertions, 2 deletions

diff --git a/llvm/test/CodeGen/X86/select.ll b/llvm/test/CodeGen/X86/select.ll
index 9df23f17468..ce04e07854a 100644
--- a/llvm/test/CodeGen/X86/select.ll
+++ b/llvm/test/CodeGen/X86/select.ll
@@ -197,7 +197,24 @@ entry:
 
 declare { i64, i1 } @llvm.umul.with.overflow.i64(i64, i64) nounwind readnone
 
+define i32 @test13(i32 %a, i32 %b) nounwind {
+  %c = icmp ult i32 %a, %b
+  %d = sext i1 %c to i32
+  ret i32 %d
+; CHECK: test13:
+; CHECK: cmpl
+; CHECK-NEXT: sbbl
+; CHECK-NEXT: ret
+}
 
-
-
+define i32 @test14(i32 %a, i32 %b) nounwind {
+  %c = icmp uge i32 %a, %b
+  %d = sext i1 %c to i32
+  ret i32 %d
+; CHECK: test14:
+; CHECK: cmpl
+; CHECK-NEXT: sbbl
+; CHECK-NEXT: notl
+; CHECK-NEXT: ret
+}