Successfully identified regression in *gcc* in CI configuration
tcwg_gnu_native_build/master-aarch64. So far, this commit has regressed CI
configurations:
- tcwg_gnu_native_build/master-aarch64
Culprit:
<cut>
commit cad36f38576a6a781e3c62ab061c68f5b8dab13a
Author: Roger Sayle <ro...@nextmovesoftware.com>
Date: Tue Aug 31 11:45:07 2021 +0100
Preserve SUBREG_PROMOTED_VAR_P on (extend:HI (subreg/s:QI (reg:SI))).
SUBREG_PROMOTED_VAR_P is a mechanism for tracking that a partial subreg
is correctly zero-extended or sign-extended in the parent register. For
example, the RTL (subreg/s/v:QI (reg/v:SI 23 [ x ]) 0) indicates that the
byte x is zero extended in reg:SI 23, which is useful for optimization.
An example is that zero extending the above QImode value to HImode can
simply use a wider subreg, i.e. (subreg:HI (reg/v:SI 23 [ x ]) 0).
This patch addresses the oversight/missed optimization opportunity that
the new HImode subreg above should retain its SUBREG_PROMOTED_VAR_P
annotation as its value is guaranteed to be correctly extended in the
SImode parent. The code below to preserve SUBREG_PROMOTED_VAR_P is already
present in the middle-end (e.g. simplify-rtx.c:7232-7242) but missing
from one or two (precisely three) places that (accidentally) strip it.
Whilst there I also added another optimization. If we need to extend
the above QImode value beyond the SImode register holding it, say to
DImode, we can eliminate the SUBREG and simply extend from the SImode
register to DImode.
2021-08-31 Roger Sayle <ro...@nextmovesoftware.com>
gcc/ChangeLog
* expr.c (convert_modes): Preserve SUBREG_PROMOTED_VAR_P when
creating a (wider) partial subreg from a SUBREG_PROMOTED_VAR_P
subreg.
* simplify-rtx.c (simplify_unary_operation_1) [SIGN_EXTEND]:
Likewise, preserve SUBREG_PROMOTED_VAR_P when creating a (wider)
partial subreg from a SUBREG_PROMOTED_VAR_P subreg. Generate
SIGN_EXTEND of the SUBREG_REG when a subreg would be paradoxical.
[ZERO_EXTEND]: Likewise, preserve SUBREG_PROMOTED_VAR_P when
creating a (wider) partial subreg from a SUBREG_PROMOTED_VAR_P
subreg. Generate ZERO_EXTEND of the SUBREG_REG when a subreg
would be paradoxical.
</cut>
Results regressed to (for first_bad == cad36f38576a6a781e3c62ab061c68f5b8dab13a)
# reset_artifacts:
-10
# true:
0
# build_abe binutils:
1
# First few build errors in logs:
# 00:05:59
/home/tcwg-buildslave/workspace/tcwg_gnu_6/abe/snapshots/gcc.git~master/libgcc/soft-fp/op-2.h:249:37:
internal compiler error: in subreg_promoted_mode, at rtl.h:3132
# 00:05:59
/home/tcwg-buildslave/workspace/tcwg_gnu_6/abe/snapshots/gcc.git~master/libgcc/soft-fp/op-2.h:249:37:
internal compiler error: in subreg_promoted_mode, at rtl.h:3132
# 00:05:59
/home/tcwg-buildslave/workspace/tcwg_gnu_6/abe/snapshots/gcc.git~master/libgcc/soft-fp/op-2.h:249:37:
internal compiler error: in subreg_promoted_mode, at rtl.h:3132
# 00:05:59
/home/tcwg-buildslave/workspace/tcwg_gnu_6/abe/snapshots/gcc.git~master/libgcc/soft-fp/op-1.h:127:36:
internal compiler error: in subreg_promoted_mode, at rtl.h:3132
# 00:05:59
/home/tcwg-buildslave/workspace/tcwg_gnu_6/abe/snapshots/gcc.git~master/libgcc/soft-fp/op-1.h:127:36:
internal compiler error: in subreg_promoted_mode, at rtl.h:3132
# 00:05:59
/home/tcwg-buildslave/workspace/tcwg_gnu_6/abe/snapshots/gcc.git~master/libgcc/soft-fp/op-2.h:249:37:
internal compiler error: in subreg_promoted_mode, at rtl.h:3132
# 00:05:59
/home/tcwg-buildslave/workspace/tcwg_gnu_6/abe/snapshots/gcc.git~master/libgcc/soft-fp/op-2.h:249:37:
internal compiler error: in subreg_promoted_mode, at rtl.h:3132
# 00:05:59
/home/tcwg-buildslave/workspace/tcwg_gnu_6/abe/snapshots/gcc.git~master/libgcc/soft-fp/op-1.h:127:36:
internal compiler error: in subreg_promoted_mode, at rtl.h:3132
# 00:05:59
/home/tcwg-buildslave/workspace/tcwg_gnu_6/abe/snapshots/gcc.git~master/libgcc/soft-fp/op-2.h:249:37:
internal compiler error: in subreg_promoted_mode, at rtl.h:3132
# 00:05:59 make[2]: ***
[/home/tcwg-buildslave/workspace/tcwg_gnu_6/abe/snapshots/gcc.git~master/libgcc/shared-object.mk:14:
trunctfhf2.o] Error 1
from (for last_good == 0960d937d9bee3c831d0b64a9c828c263a58ff89)
# reset_artifacts:
-10
# true:
0
# build_abe binutils:
1
# build_abe gcc:
2
# build_abe linux:
4
# build_abe glibc:
5
# build_abe gdb:
6
Artifacts of last_good build:
https://ci.linaro.org/job/tcwg_gnu_native_build-bisect-master-aarch64/1/artifact/artifacts/build-0960d937d9bee3c831d0b64a9c828c263a58ff89/
Artifacts of first_bad build:
https://ci.linaro.org/job/tcwg_gnu_native_build-bisect-master-aarch64/1/artifact/artifacts/build-cad36f38576a6a781e3c62ab061c68f5b8dab13a/
Build top page/logs:
https://ci.linaro.org/job/tcwg_gnu_native_build-bisect-master-aarch64/1/
Configuration details:
Reproduce builds:
<cut>
mkdir investigate-gcc-cad36f38576a6a781e3c62ab061c68f5b8dab13a
cd investigate-gcc-cad36f38576a6a781e3c62ab061c68f5b8dab13a
git clone https://git.linaro.org/toolchain/jenkins-scripts
mkdir -p artifacts/manifests
curl -o artifacts/manifests/build-baseline.sh
https://ci.linaro.org/job/tcwg_gnu_native_build-bisect-master-aarch64/1/artifact/artifacts/manifests/build-baseline.sh
--fail
curl -o artifacts/manifests/build-parameters.sh
https://ci.linaro.org/job/tcwg_gnu_native_build-bisect-master-aarch64/1/artifact/artifacts/manifests/build-parameters.sh
--fail
curl -o artifacts/test.sh
https://ci.linaro.org/job/tcwg_gnu_native_build-bisect-master-aarch64/1/artifact/artifacts/test.sh
--fail
chmod +x artifacts/test.sh
# Reproduce the baseline build (build all pre-requisites)
./jenkins-scripts/tcwg_gnu-build.sh @@ artifacts/manifests/build-baseline.sh
# Save baseline build state (which is then restored in artifacts/test.sh)
mkdir -p ./bisect
rsync -a --del --delete-excluded --exclude /bisect/ --exclude /artifacts/
--exclude /gcc/ ./ ./bisect/baseline/
cd gcc
# Reproduce first_bad build
git checkout --detach cad36f38576a6a781e3c62ab061c68f5b8dab13a
../artifacts/test.sh
# Reproduce last_good build
git checkout --detach 0960d937d9bee3c831d0b64a9c828c263a58ff89
../artifacts/test.sh
cd ..
</cut>
History of pending regressions and results:
https://git.linaro.org/toolchain/ci/base-artifacts.git/log/?h=linaro-local/ci/tcwg_gnu_native_build/master-aarch64
Artifacts:
https://ci.linaro.org/job/tcwg_gnu_native_build-bisect-master-aarch64/1/artifact/artifacts/
Build log:
https://ci.linaro.org/job/tcwg_gnu_native_build-bisect-master-aarch64/1/consoleText
Full commit (up to 1000 lines):
<cut>
commit cad36f38576a6a781e3c62ab061c68f5b8dab13a
Author: Roger Sayle <ro...@nextmovesoftware.com>
Date: Tue Aug 31 11:45:07 2021 +0100
Preserve SUBREG_PROMOTED_VAR_P on (extend:HI (subreg/s:QI (reg:SI))).
SUBREG_PROMOTED_VAR_P is a mechanism for tracking that a partial subreg
is correctly zero-extended or sign-extended in the parent register. For
example, the RTL (subreg/s/v:QI (reg/v:SI 23 [ x ]) 0) indicates that the
byte x is zero extended in reg:SI 23, which is useful for optimization.
An example is that zero extending the above QImode value to HImode can
simply use a wider subreg, i.e. (subreg:HI (reg/v:SI 23 [ x ]) 0).
This patch addresses the oversight/missed optimization opportunity that
the new HImode subreg above should retain its SUBREG_PROMOTED_VAR_P
annotation as its value is guaranteed to be correctly extended in the
SImode parent. The code below to preserve SUBREG_PROMOTED_VAR_P is already
present in the middle-end (e.g. simplify-rtx.c:7232-7242) but missing
from one or two (precisely three) places that (accidentally) strip it.
Whilst there I also added another optimization. If we need to extend
the above QImode value beyond the SImode register holding it, say to
DImode, we can eliminate the SUBREG and simply extend from the SImode
register to DImode.
2021-08-31 Roger Sayle <ro...@nextmovesoftware.com>
gcc/ChangeLog
* expr.c (convert_modes): Preserve SUBREG_PROMOTED_VAR_P when
creating a (wider) partial subreg from a SUBREG_PROMOTED_VAR_P
subreg.
* simplify-rtx.c (simplify_unary_operation_1) [SIGN_EXTEND]:
Likewise, preserve SUBREG_PROMOTED_VAR_P when creating a (wider)
partial subreg from a SUBREG_PROMOTED_VAR_P subreg. Generate
SIGN_EXTEND of the SUBREG_REG when a subreg would be paradoxical.
[ZERO_EXTEND]: Likewise, preserve SUBREG_PROMOTED_VAR_P when
creating a (wider) partial subreg from a SUBREG_PROMOTED_VAR_P
subreg. Generate ZERO_EXTEND of the SUBREG_REG when a subreg
would be paradoxical.
---
gcc/expr.c | 19 ++++++++++++++++++-
gcc/simplify-rtx.c | 52 ++++++++++++++++++++++++++++++++++++++++++----------
2 files changed, 60 insertions(+), 11 deletions(-)
diff --git a/gcc/expr.c b/gcc/expr.c
index 096c0315ecc..5dd98a9bccc 100644
--- a/gcc/expr.c
+++ b/gcc/expr.c
@@ -688,7 +688,24 @@ convert_modes (machine_mode mode, machine_mode oldmode,
rtx x, int unsignedp)
&& (GET_MODE_PRECISION (subreg_promoted_mode (x))
>= GET_MODE_PRECISION (int_mode))
&& SUBREG_CHECK_PROMOTED_SIGN (x, unsignedp))
- x = gen_lowpart (int_mode, SUBREG_REG (x));
+ {
+ scalar_int_mode int_orig_mode;
+ machine_mode orig_mode = GET_MODE (x);
+ x = gen_lowpart (int_mode, SUBREG_REG (x));
+
+ /* Preserve SUBREG_PROMOTED_VAR_P if the new mode is wider than
+ the original mode, but narrower than the inner mode. */
+ if (GET_CODE (x) == SUBREG
+ && GET_MODE_PRECISION (subreg_promoted_mode (x))
+ > GET_MODE_PRECISION (int_mode)
+ && is_a <scalar_int_mode> (orig_mode, &int_orig_mode)
+ && GET_MODE_PRECISION (int_mode)
+ > GET_MODE_PRECISION (int_orig_mode))
+ {
+ SUBREG_PROMOTED_VAR_P (x) = 1;
+ SUBREG_PROMOTED_SET (x, unsignedp);
+ }
+ }
if (GET_MODE (x) != VOIDmode)
oldmode = GET_MODE (x);
diff --git a/gcc/simplify-rtx.c b/gcc/simplify-rtx.c
index e431e0c19d7..ebad5cb5a79 100644
--- a/gcc/simplify-rtx.c
+++ b/gcc/simplify-rtx.c
@@ -1512,12 +1512,28 @@ simplify_context::simplify_unary_operation_1 (rtx_code
code, machine_mode mode,
target mode is the same as the variable's promotion. */
if (GET_CODE (op) == SUBREG
&& SUBREG_PROMOTED_VAR_P (op)
- && SUBREG_PROMOTED_SIGNED_P (op)
- && !paradoxical_subreg_p (mode, GET_MODE (SUBREG_REG (op))))
+ && SUBREG_PROMOTED_SIGNED_P (op))
{
- temp = rtl_hooks.gen_lowpart_no_emit (mode, SUBREG_REG (op));
- if (temp)
- return temp;
+ rtx subreg = SUBREG_REG (op);
+ machine_mode subreg_mode = GET_MODE (subreg);
+ if (!paradoxical_subreg_p (mode, subreg_mode))
+ {
+ temp = rtl_hooks.gen_lowpart_no_emit (mode, subreg);
+ if (temp)
+ {
+ /* Preserve SUBREG_PROMOTED_VAR_P. */
+ if (partial_subreg_p (temp))
+ {
+ SUBREG_PROMOTED_VAR_P (temp) = 1;
+ SUBREG_PROMOTED_SET (temp, 1);
+ }
+ return temp;
+ }
+ }
+ else
+ /* Sign-extending a sign-extended subreg. */
+ return simplify_gen_unary (SIGN_EXTEND, mode,
+ subreg, subreg_mode);
}
/* (sign_extend:M (sign_extend:N <X>)) is (sign_extend:M <X>).
@@ -1631,12 +1647,28 @@ simplify_context::simplify_unary_operation_1 (rtx_code
code, machine_mode mode,
target mode is the same as the variable's promotion. */
if (GET_CODE (op) == SUBREG
&& SUBREG_PROMOTED_VAR_P (op)
- && SUBREG_PROMOTED_UNSIGNED_P (op)
- && !paradoxical_subreg_p (mode, GET_MODE (SUBREG_REG (op))))
+ && SUBREG_PROMOTED_UNSIGNED_P (op))
{
- temp = rtl_hooks.gen_lowpart_no_emit (mode, SUBREG_REG (op));
- if (temp)
- return temp;
+ rtx subreg = SUBREG_REG (op);
+ machine_mode subreg_mode = GET_MODE (subreg);
+ if (!paradoxical_subreg_p (mode, subreg_mode))
+ {
+ temp = rtl_hooks.gen_lowpart_no_emit (mode, subreg);
+ if (temp)
+ {
+ /* Preserve SUBREG_PROMOTED_VAR_P. */
+ if (partial_subreg_p (temp))
+ {
+ SUBREG_PROMOTED_VAR_P (temp) = 1;
+ SUBREG_PROMOTED_SET (temp, 0);
+ }
+ return temp;
+ }
+ }
+ else
+ /* Zero-extending a zero-extended subreg. */
+ return simplify_gen_unary (ZERO_EXTEND, mode,
+ subreg, subreg_mode);
}
/* Extending a widening multiplication should be canonicalized to
</cut>
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