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| author | Keith Randall <khr@golang.org> | 2025-11-04 15:15:16 -0800 |
|---|---|---|
| committer | Gopher Robot <gobot@golang.org> | 2025-11-10 09:34:13 -0800 |
| commit | 3b3d6b9e5d9898810ee13e739f3ad759ab104fdb (patch) | |
| tree | 167486b89c8c153d560836065874f4d54829169d /src/cmd/asm/internal | |
| parent | 5f4b5f1a196774e45bc50de0729973119eb7bf07 (diff) | |
| download | go-3b3d6b9e5d9898810ee13e739f3ad759ab104fdb.tar.xz | |
cmd/internal/obj/arm64: shorten constant integer loads
Large integer constants can take up to 4 instructions to encode.
We can encode some large constants with a single instruction, namely
those which are bit patterns (repetitions of certain runs of 0s and 1s).
Often the constants we want to encode are *close* to those bit patterns,
but don't exactly match. For those, we can use 2 instructions, one to
load the close-by bit pattern and one to fix up any mismatches.
The constants we use to strength reduce divides often fit this pattern.
For unsigned divides by 1 through 15, this CL applies to the constant
for N=3,5,6,10,12,15.
Triggers 17 times in hello world.
Change-Id: I623abf32961fb3e74d0a163f6822f0647cd94499
Reviewed-on: https://go-review.googlesource.com/c/go/+/717900
Auto-Submit: Keith Randall <khr@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Keith Randall <khr@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Diffstat (limited to 'src/cmd/asm/internal')
| -rw-r--r-- | src/cmd/asm/internal/asm/testdata/arm64.s | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/src/cmd/asm/internal/asm/testdata/arm64.s b/src/cmd/asm/internal/asm/testdata/arm64.s index ae10f347bb..773380e9bb 100644 --- a/src/cmd/asm/internal/asm/testdata/arm64.s +++ b/src/cmd/asm/internal/asm/testdata/arm64.s @@ -400,6 +400,8 @@ TEXT foo(SB), DUPOK|NOSPLIT, $-8 MOVD $0x11110000, R1 // MOVD $286326784, R1 // 2122a2d2 MOVD $0xaaaa0000aaaa1111, R1 // MOVD $-6149102338357718767, R1 // 212282d24155b5f24155f5f2 MOVD $0x1111ffff1111aaaa, R1 // MOVD $1230045644216969898, R1 // a1aa8a922122a2f22122e2f2 + MOVD $0xaaaaaaaaaaaaaaab, R1 // MOVD $-6148914691236517205, R1 // e1f301b2615595f2 + MOVD $0x0ff019940ff00ff0, R1 // MOVD $1148446028692721648, R1 // e19f0cb28132c3f2 MOVD $0, R1 // e1031faa MOVD $-1, R1 // 01008092 MOVD $0x210000, R0 // MOVD $2162688, R0 // 2004a0d2 |