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| author | Roger Sayle <roger@nextmovesoftware.com> | 2020-08-10 21:09:16 +0100 |
|---|---|---|
| committer | Roger Sayle <roger@nextmovesoftware.com> | 2020-08-10 21:09:16 +0100 |
| commit | e4ced0b60ccb4c944970304cf74f1ee9086e5553 (patch) | |
| tree | 0f3ec10bf03fe8509f8c53efa60e2623d08f3800 /gcc | |
| parent | 5b065f0563262a0d6cd1fea8426913bfdd841301 (diff) | |
| download | gcc-e4ced0b60ccb4c944970304cf74f1ee9086e5553.zip gcc-e4ced0b60ccb4c944970304cf74f1ee9086e5553.tar.gz gcc-e4ced0b60ccb4c944970304cf74f1ee9086e5553.tar.bz2 | |
i386: Improve code generation of smin(x,0) with -m32.
To make amends for the recent (temporary) testsuite failure
of my new gcc.target/i386/minmax-9.c when compiled with -m32,
this patch improves the -m32 code we generate for the examples
in that test case.
The trick is to expand smin(x,0) as "x < 0 ? x : 0" instead
of the current "x <= 0 ? x : 0", as the former can take
advantage of sign_bit_mask operations.
2020-08-10 Roger Sayle <roger@nextmovesoftware.com>
gcc/ChangeLog
* config/i386/i386-expand.c (ix86_expand_int_movcc): Expand
signed MIN_EXPR against zero as "x < 0 ? x : 0" instead of
"x <= 0 ? x : 0" to enable sign_bit_compare_p optimizations.
gcc/testsuite/ChangeLog
* gcc.target/i386/minmax-12.c: New test.
Diffstat (limited to 'gcc')
| -rw-r--r-- | gcc/config/i386/i386-expand.c | 12 | ||||
| -rw-r--r-- | gcc/testsuite/gcc.target/i386/minmax-12.c | 17 |
2 files changed, 28 insertions, 1 deletions
diff --git a/gcc/config/i386/i386-expand.c b/gcc/config/i386/i386-expand.c index 1bd0df4..f441ba9 100644 --- a/gcc/config/i386/i386-expand.c +++ b/gcc/config/i386/i386-expand.c @@ -3305,7 +3305,17 @@ ix86_expand_int_movcc (rtx operands[]) { var = operands[2]; if (INTVAL (operands[3]) == 0 && operands[2] != constm1_rtx) - operands[2] = constm1_rtx, op = and_optab; + { + /* For smin (x, 0), expand as "x < 0 ? x : 0" instead of + "x <= 0 ? x : 0" to enable sign_bit_compare_p. */ + if (code == LE && op1 == const0_rtx && rtx_equal_p (op0, var)) + operands[1] = simplify_gen_relational (LT, VOIDmode, + GET_MODE (op0), + op0, const0_rtx); + + operands[2] = constm1_rtx; + op = and_optab; + } else if (INTVAL (operands[3]) == -1 && operands[3] != const0_rtx) operands[2] = const0_rtx, op = ior_optab; else diff --git a/gcc/testsuite/gcc.target/i386/minmax-12.c b/gcc/testsuite/gcc.target/i386/minmax-12.c new file mode 100644 index 0000000..40efe54 --- /dev/null +++ b/gcc/testsuite/gcc.target/i386/minmax-12.c @@ -0,0 +1,17 @@ +/* { dg-do compile { target ia32 } } */ +/* { dg-options "-O2 -march=i386 -mtune=generic" } */ + +#define min(a,b) (((a) < (b))? (a) : (b)) + +int foo(int x) +{ + return min(x,0); +} + +signed char bar(signed char x) +{ + return min(x,0); +} + +/* { dg-final { scan-assembler "cltd" } } */ +/* { dg-final { scan-assembler "sarb" } } */ |