File: 2009-05-23-dagcombine-shifts.ll

package info (click to toggle)
llvm-toolchain-11 1%3A11.0.1-2
  • links: PTS, VCS
  • area: main
  • in suites: bullseye
  • size: 995,808 kB
  • sloc: cpp: 4,767,656; ansic: 760,916; asm: 477,436; python: 170,940; objc: 69,804; lisp: 29,914; sh: 23,855; f90: 18,173; pascal: 7,551; perl: 7,471; ml: 5,603; awk: 3,489; makefile: 2,573; xml: 915; cs: 573; fortran: 503; javascript: 452
file content (28 lines) | stat: -rw-r--r-- 783 bytes parent folder | download | duplicates (25) 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
 
; RUN: llc < %s | FileCheck %s

; Check that the shr(shl X, 56), 48) is not mistakenly turned into
; a shr (X, -8) that gets subsequently "optimized away" as undef
; PR4254

; after fixing PR24373
; shlq $56, %rdi
; sarq $48, %rdi
; folds into
; movsbq %dil, %rax
; shlq $8, %rax
; which is better for x86

target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128"
target triple = "x86_64-unknown-linux-gnu"

define i64 @foo(i64 %b) nounwind readnone {
entry:
; CHECK-LABEL: foo:
; CHECK: movsbq %dil, %rax
; CHECK: shlq $8, %rax
; CHECK: orq $1, %rax
	%shl = shl i64 %b, 56		; <i64> [#uses=1]
	%shr = ashr i64 %shl, 48		; <i64> [#uses=1]
	%add5 = or i64 %shr, 1		; <i64> [#uses=1]
	ret i64 %add5
}