The MIPS32 architecture supports madd, msub, nmadd, and nmsub instructions
as well as rsqrt and recip instructions even when it doesn't have a 64 bit
floating point unit. This was not clear in the original MIPS32 architecture
document (MD00086) but was clarified in 2011 (version 3.0.2, March 21, 2011).
This patch updates the ISA_HAS_FP4 and ISA_HAS_NMADD4_NMSUB4 macros and the
recip_condition mode attribute to allow the use of these instructions for all
MIPS32 architectures (with or without FLOAT64).
Testing showed one new test failure (gcc.target/mips/rsqrt-4.c) which I
updated to reflect that we can now generate and use a rsqrt.d instruction.
I put Chao-ying and Maciej's names on the patch since they did the
original changes in GCC but those changes were never checked in upstream.
OK to checkin?
Steve Ellcey
sell...@mips.com
In the spec MD00086, page 347 Revision History, 3.0.2, March 21, 2011, RECIP, R
SQRT instructions do not require 64-bit FPU.
2012-12-12 Steve Ellcey <sell...@mips.com>
Chao-ying Fu <f...@mips.com>
Maciej W. Rozycki <ma...@codesourcery.com>
* config/mips/mips.h (ISA_HAS_FP4): Allow madd, etc. on all MIPS32R2.
(ISA_HAS_NMADD4_NMSUB4): Ditto.
* config/mips/mips.md (recip_condition): Allow recip and rsqrt on
all MIPS32R2.
diff --git a/gcc/config/mips/mips.h b/gcc/config/mips/mips.h
index 60b26cb..44874e9 100644
--- a/gcc/config/mips/mips.h
+++ b/gcc/config/mips/mips.h
@@ -858,7 +858,7 @@ struct mips_cpu_info {
FP madd and msub instructions, and the FP recip and recip sqrt
instructions. */
#define ISA_HAS_FP4 ((ISA_MIPS4 \
- || (ISA_MIPS32R2 && TARGET_FLOAT64) \
+ || ISA_MIPS32R2 \
|| ISA_MIPS64 \
|| ISA_MIPS64R2) \
&& !TARGET_MIPS16)
@@ -889,10 +889,7 @@ struct mips_cpu_info {
/* ISA has floating-point nmadd and nmsub instructions
'd = -((a * b) [+-] c)'. */
#define ISA_HAS_NMADD4_NMSUB4(MODE) \
- ((ISA_MIPS4 \
- || (ISA_MIPS32R2 && (MODE) == V2SFmode) \
- || ISA_MIPS64 \
- || ISA_MIPS64R2) \
+ (ISA_HAS_FP4 \
&& (!TARGET_MIPS5400 || TARGET_MAD) \
&& !TARGET_MIPS16)
diff --git a/gcc/config/mips/mips.md b/gcc/config/mips/mips.md
index a3aa922..796597e 100644
--- a/gcc/config/mips/mips.md
+++ b/gcc/config/mips/mips.md
@@ -858,12 +858,10 @@
[(SF "!ISA_MIPS1") (DF "!ISA_MIPS1") (V2SF "TARGET_SB1")])
;; This attribute gives the conditions under which RECIP.fmt and RSQRT.fmt
-;; instructions can be used. The MIPS32 and MIPS64 ISAs say that RECIP.D
-;; and RSQRT.D are unpredictable when doubles are stored in pairs of FPRs,
-;; so for safety's sake, we apply this restriction to all targets.
+;; instructions can be used.
(define_mode_attr recip_condition
[(SF "ISA_HAS_FP4")
- (DF "ISA_HAS_FP4 && TARGET_FLOAT64")
+ (DF "ISA_HAS_FP4")
(V2SF "TARGET_SB1")])
;; This code iterator allows signed and unsigned widening multiplications
============= Test change ===========
2012-12-12 Steve Ellcey <sell...@mips.com>
* gcc.target/mips/rsqrt-4.c: Update to show use of sqrt.d.
diff --git a/gcc/testsuite/gcc.target/mips/rsqrt-4.c
b/gcc/testsuite/gcc.target/mips/rsqrt-4.c
index 6b6577e..471dd28 100644
--- a/gcc/testsuite/gcc.target/mips/rsqrt-4.c
+++ b/gcc/testsuite/gcc.target/mips/rsqrt-4.c
@@ -1,7 +1,7 @@
/* { dg-do compile } */
/* { dg-options "-ffast-math -mips64 -mhard-float -mgp32" } */
/* { dg-skip-if "code quality test" { *-*-* } { "-O0" } { "" } } */
-/* { dg-final { scan-assembler-not "\trsqrt.d\t" } } */
+/* { dg-final { scan-assembler-times "\trsqrt.d\t" 2 } } */
/* { dg-final { scan-assembler-times "\trsqrt.s\t" 2 } } */
extern double sqrt(double);
