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llvm-project/llvm/test/CodeGen/X86/2009-05-23-dagcombine-shift...

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Select an OR with immediate as an ADD if the input bits are known zero. This allow the instruction to be 3address-fied if needed. llvm-svn: 93152
2010-01-12 01:03:47 +08:00
; RUN: llc < %s | FileCheck %s
Fix PR4254. The DAGCombiner created a negative shiftamount, stored in an unsigned variable. Later the optimizer eliminated the shift entirely as being undefined. Example: (srl (shl X, 56) 48). ShiftAmt is 4294967288. Fix it by checking that the shiftamount is positive, and storing in a signed variable. llvm-svn: 72331
2009-05-24 01:29:48 +08:00
; 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
Select an OR with immediate as an ADD if the input bits are known zero. This allow the instruction to be 3address-fied if needed. llvm-svn: 93152
2010-01-12 01:03:47 +08:00
[X86] Improve shift combining This folds (ashr (shl a, [56,48,32,24,16]), SarConst) into (shl, (sext (a), [56,48,32,24,16] - SarConst)) or into (lshr, (sext (a), SarConst - [56,48,32,24,16])) depending on sign of (SarConst - [56,48,32,24,16]) sexts in X86 are MOVs. The MOVs have the same code size as above SHIFTs (only SHIFT by 1 has lower code size). However the MOVs have 2 advantages to SHIFTs on x86: 1. MOVs can write to a register that differs from source. 2. MOVs accept memory operands. This fixes PR24373. Patch by: evgeny.v.stupachenko@intel.com Differential Revision: http://reviews.llvm.org/D13161 llvm-svn: 255761
2015-12-16 19:22:37 +08:00
; after fixing PR24373
; shlq $56, %rdi
; sarq $48, %rdi
; folds into
; movsbq %dil, %rax
; shlq $8, %rax
; which is better for x86
Fix PR4254. The DAGCombiner created a negative shiftamount, stored in an unsigned variable. Later the optimizer eliminated the shift entirely as being undefined. Example: (srl (shl X, 56) 48). ShiftAmt is 4294967288. Fix it by checking that the shiftamount is positive, and storing in a signed variable. llvm-svn: 72331
2009-05-24 01:29:48 +08:00
target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128"
target triple = "x86_64-unknown-linux-gnu"
define i64 @foo(i64 %b) nounwind readnone {
entry:
Mass update to CodeGen tests to use CHECK-LABEL for labels corresponding to function definitions for more informative error messages. No functionality change and all updated tests passed locally. This update was done with the following bash script: find test/CodeGen -name "*.ll" | \ while read NAME; do echo "$NAME" if ! grep -q "^; *RUN: *llc.*debug" $NAME; then TEMP=`mktemp -t temp` cp $NAME $TEMP sed -n "s/^define [^@]*@\([A-Za-z0-9_]*\)(.*$/\1/p" < $NAME | \ while read FUNC; do sed -i '' "s/;\(.*\)\([A-Za-z0-9_-]*\):\( *\)$FUNC: *\$/;\1\2-LABEL:\3$FUNC:/g" $TEMP done sed -i '' "s/;\(.*\)-LABEL-LABEL:/;\1-LABEL:/" $TEMP sed -i '' "s/;\(.*\)-NEXT-LABEL:/;\1-NEXT:/" $TEMP sed -i '' "s/;\(.*\)-NOT-LABEL:/;\1-NOT:/" $TEMP sed -i '' "s/;\(.*\)-DAG-LABEL:/;\1-DAG:/" $TEMP mv $TEMP $NAME fi done llvm-svn: 186280
2013-07-14 14:24:09 +08:00
; CHECK-LABEL: foo:
[X86] Improve shift combining This folds (ashr (shl a, [56,48,32,24,16]), SarConst) into (shl, (sext (a), [56,48,32,24,16] - SarConst)) or into (lshr, (sext (a), SarConst - [56,48,32,24,16])) depending on sign of (SarConst - [56,48,32,24,16]) sexts in X86 are MOVs. The MOVs have the same code size as above SHIFTs (only SHIFT by 1 has lower code size). However the MOVs have 2 advantages to SHIFTs on x86: 1. MOVs can write to a register that differs from source. 2. MOVs accept memory operands. This fixes PR24373. Patch by: evgeny.v.stupachenko@intel.com Differential Revision: http://reviews.llvm.org/D13161 llvm-svn: 255761
2015-12-16 19:22:37 +08:00
; CHECK: movsbq %dil, %rax
; CHECK: shlq $8, %rax
; CHECK: orq $1, %rax
Fix PR4254. The DAGCombiner created a negative shiftamount, stored in an unsigned variable. Later the optimizer eliminated the shift entirely as being undefined. Example: (srl (shl X, 56) 48). ShiftAmt is 4294967288. Fix it by checking that the shiftamount is positive, and storing in a signed variable. llvm-svn: 72331
2009-05-24 01:29:48 +08:00
%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
}