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| author | Isaac Chen <ycchen@google.com> | 2017-06-26 20:23:26 +0800 |
|---|---|---|
| committer | Isaac Chen <ycchen@google.com> | 2017-08-21 11:23:04 +0800 |
| commit | 451e99bae63bc3f06e3b01e8d32a7ec1416b3d2f (patch) | |
| tree | 408fa8b62a9ed08799e0388d8cbf44f090007f9f | |
| parent | 68ab54444a2da7e11cdd3c35a87a72430f4051ac (diff) | |
| download | bionic-451e99bae63bc3f06e3b01e8d32a7ec1416b3d2f.tar.gz | |
Build support for 32-bit armv8-a
The assembly in arm's generic strlen implementation contains deprecated
instruction sequence:
it eq ; start of IT block
ldreq ... ; 32-bit T32 insruction in IT block deprecated in armv8
This will cause compiler error because of -Winline-asm and -Werror.
The fix here is to change the sequence:
it eq
ldreq ...
bne 1f
to equivalent sequence:
bne 1f
ldr ...
The resulted sequence is (1 instruction) shorter.
See ARM for ARMv8 for details:
F6.2 Partial Deprecation of IT
... All uses of IT that apply to instructions other than a single
subsequent 16-bit instruction from a restricted set are deprecated, ...
Bug: 62895439
Test: "bionic-unit-tests-static --gtest_filter=*strlen*" on Nexus 4
(krait), emulator (armv7), and sailfish (armv8).
The test binary for the first 2 is built with armv7-a as its
TARGET_CPU_ARCH; The test binary for the last is built with
armv8-a as its TARGET_2ND_CPU_ARCH.
TARGET(_2ND)_CPU_VARIANTs of both binaries are set to "generic".
Change-Id: Ia2208b4e2ba2cad589975bc7b4617688cbb8826a
Merged-Id: Ia2208b4e2ba2cad589975bc7b4617688cbb8826a
(cherry picked from commit d544fb7da025b805b6e9dd61c4bfabb9272271b2)
| -rw-r--r-- | libc/arch-arm/generic/bionic/strlen.c | 29 |
1 files changed, 11 insertions, 18 deletions
diff --git a/libc/arch-arm/generic/bionic/strlen.c b/libc/arch-arm/generic/bionic/strlen.c index f6b920937..dccd56448 100644 --- a/libc/arch-arm/generic/bionic/strlen.c +++ b/libc/arch-arm/generic/bionic/strlen.c @@ -67,53 +67,46 @@ size_t strlen(const char *s) __overloadable "sub %[t], %[v], %[mask], lsr #7\n" "and %[t], %[t], %[mask] \n" "bics %[t], %[t], %[v] \n" - "it eq \n" - "ldreq %[v], [%[s]], #4 \n" -#if !defined(__OPTIMIZE_SIZE__) "bne 1f \n" + "ldr %[v], [%[s]], #4 \n" +#if !defined(__OPTIMIZE_SIZE__) "sub %[t], %[v], %[mask], lsr #7\n" "and %[t], %[t], %[mask] \n" "bics %[t], %[t], %[v] \n" - "it eq \n" - "ldreq %[v], [%[s]], #4 \n" "bne 1f \n" + "ldr %[v], [%[s]], #4 \n" "sub %[t], %[v], %[mask], lsr #7\n" "and %[t], %[t], %[mask] \n" "bics %[t], %[t], %[v] \n" - "it eq \n" - "ldreq %[v], [%[s]], #4 \n" "bne 1f \n" + "ldr %[v], [%[s]], #4 \n" "sub %[t], %[v], %[mask], lsr #7\n" "and %[t], %[t], %[mask] \n" "bics %[t], %[t], %[v] \n" - "it eq \n" - "ldreq %[v], [%[s]], #4 \n" "bne 1f \n" + "ldr %[v], [%[s]], #4 \n" "sub %[t], %[v], %[mask], lsr #7\n" "and %[t], %[t], %[mask] \n" "bics %[t], %[t], %[v] \n" - "it eq \n" - "ldreq %[v], [%[s]], #4 \n" "bne 1f \n" + "ldr %[v], [%[s]], #4 \n" "sub %[t], %[v], %[mask], lsr #7\n" "and %[t], %[t], %[mask] \n" "bics %[t], %[t], %[v] \n" - "it eq \n" - "ldreq %[v], [%[s]], #4 \n" "bne 1f \n" + "ldr %[v], [%[s]], #4 \n" "sub %[t], %[v], %[mask], lsr #7\n" "and %[t], %[t], %[mask] \n" "bics %[t], %[t], %[v] \n" - "it eq \n" - "ldreq %[v], [%[s]], #4 \n" "bne 1f \n" + "ldr %[v], [%[s]], #4 \n" "sub %[t], %[v], %[mask], lsr #7\n" "and %[t], %[t], %[mask] \n" "bics %[t], %[t], %[v] \n" - "it eq \n" - "ldreq %[v], [%[s]], #4 \n" + "bne 1f \n" + "ldr %[v], [%[s]], #4 \n" #endif - "beq 0b \n" + "b 0b \n" "1: \n" "add %[l], %[l], %[s] \n" "tst %[v], #0xFF \n" |