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eda4e2e4a7
AMD's processors family K7, K8, K10, K12, K15 and K16 are known to have SHLD/SHRD instructions with very poor latency. Optimization guides for these processors recommend using an alternative sequence of instructions. For these AMD's processors, I disabled folding (or (x << c) | (y >> (64 - c))) when we are not optimizing for size. It might be beneficial to disable this folding for some of the Intel's processors. However, since I couldn't find specific recommendations regarding using SHLD/SHRD instructions on Intel's processors, I haven't disabled this peephole for Intel. llvm-svn: 195383
78 lines
1.9 KiB
LLVM
78 lines
1.9 KiB
LLVM
; RUN: llc < %s -march=x86-64 -mcpu=bdver1 | FileCheck %s
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; Verify that for the architectures that are known to have poor latency
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; double precision shift instructions we generate alternative sequence
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; of instructions with lower latencies instead of shld instruction.
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;uint64_t lshift1(uint64_t a, uint64_t b)
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;{
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; return (a << 1) | (b >> 63);
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;}
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; CHECK: lshift1:
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; CHECK: addq {{.*}},{{.*}}
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; CHECK-NEXT: shrq $63, {{.*}}
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; CHECK-NEXT: leaq ({{.*}},{{.*}}), {{.*}}
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define i64 @lshift1(i64 %a, i64 %b) nounwind readnone uwtable {
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entry:
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%shl = shl i64 %a, 1
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%shr = lshr i64 %b, 63
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%or = or i64 %shr, %shl
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ret i64 %or
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}
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;uint64_t lshift2(uint64_t a, uint64_t b)
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;{
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; return (a << 2) | (b >> 62);
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;}
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; CHECK: lshift2:
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; CHECK: shlq $2, {{.*}}
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; CHECK-NEXT: shrq $62, {{.*}}
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; CHECK-NEXT: leaq ({{.*}},{{.*}}), {{.*}}
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define i64 @lshift2(i64 %a, i64 %b) nounwind readnone uwtable {
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entry:
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%shl = shl i64 %a, 2
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%shr = lshr i64 %b, 62
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%or = or i64 %shr, %shl
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ret i64 %or
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}
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;uint64_t lshift7(uint64_t a, uint64_t b)
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;{
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; return (a << 7) | (b >> 57);
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;}
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; CHECK: lshift7:
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; CHECK: shlq $7, {{.*}}
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; CHECK-NEXT: shrq $57, {{.*}}
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; CHECK-NEXT: leaq ({{.*}},{{.*}}), {{.*}}
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define i64 @lshift7(i64 %a, i64 %b) nounwind readnone uwtable {
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entry:
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%shl = shl i64 %a, 7
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%shr = lshr i64 %b, 57
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%or = or i64 %shr, %shl
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ret i64 %or
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}
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;uint64_t lshift63(uint64_t a, uint64_t b)
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;{
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; return (a << 63) | (b >> 1);
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;}
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; CHECK: lshift63:
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; CHECK: shlq $63, {{.*}}
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; CHECK-NEXT: shrq {{.*}}
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; CHECK-NEXT: leaq ({{.*}},{{.*}}), {{.*}}
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define i64 @lshift63(i64 %a, i64 %b) nounwind readnone uwtable {
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entry:
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%shl = shl i64 %a, 63
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%shr = lshr i64 %b, 1
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%or = or i64 %shr, %shl
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ret i64 %or
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}
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