llvm-mirror/test/CodeGen/X86/sdiv-exact.ll

; RUN: llc -march=x86 < %s | FileCheck %s

define i32 @test1(i32 %x) {
  %div = sdiv exact i32 %x, 25
  ret i32 %div
; CHECK: test1:
; CHECK: imull	$-1030792151, 4(%esp)
; CHECK-NEXT: ret
}

define i32 @test2(i32 %x) {
  %div = sdiv exact i32 %x, 24
  ret i32 %div
; CHECK: test2:
; CHECK: sarl	$3
; CHECK-NEXT: imull	$-1431655765
; CHECK-NEXT: ret
}
Emit a more efficient magic number multiplication for exact sdivs. We have to do this in DAGBuilder instead of DAGCombiner, because the exact bit is lost after building. struct foo { char x[24]; }; long bar(struct foo a, struct foo b) { return a-b; } is now compiled into movl 4(%esp), %eax subl 8(%esp), %eax sarl $3, %eax imull $-1431655765, %eax, %eax instead of movl 4(%esp), %eax subl 8(%esp), %eax movl $715827883, %ecx imull %ecx movl %edx, %eax shrl $31, %eax sarl $2, %edx addl %eax, %edx movl %edx, %eax llvm-svn: 134695 2011-07-08 12:31:30 +02:00			`; RUN: llc -march=x86 < %s \| FileCheck %s`

			`define i32 @test1(i32 %x) {`
			`%div = sdiv exact i32 %x, 25`
			`ret i32 %div`
			`; CHECK: test1:`
			`; CHECK: imull $-1030792151, 4(%esp)`
			`; CHECK-NEXT: ret`
			`}`

			`define i32 @test2(i32 %x) {`
			`%div = sdiv exact i32 %x, 24`
			`ret i32 %div`
			`; CHECK: test2:`
			`; CHECK: sarl $3`
			`; CHECK-NEXT: imull $-1431655765`
			`; CHECK-NEXT: ret`
			`}`