runtime/cgo, math: don't use FP instructions for soft-float mips{,le}

Updates #18162

Change-Id: I591fcf71a02678a99a56a6487da9689d3c9b1bb6
Reviewed-on: https://go-review.googlesource.com/37955
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

src/math/sqrt_mipsx.s

@@ -8,7 +8,11 @@
 
 // func Sqrt(x float64) float64
 TEXT ·Sqrt(SB),NOSPLIT,$0
+#ifdef GOMIPS_softfloat
+	JMP ·sqrt(SB)
+#else
 	MOVD	x+0(FP), F0
 	SQRTD	F0, F0
 	MOVD	F0, ret+8(FP)
+#endif
 	RET

src/runtime/cgo/asm_mipsx.s

@@ -20,7 +20,11 @@ TEXT crosscall2(SB),NOSPLIT,$-4
 
 	// Space for 9 caller-saved GPR + LR + 6 caller-saved FPR.
 	// O32 ABI allows us to smash 16 bytes argument area of caller frame.
+#ifndef GOMIPS_softfloat
 	SUBU	$(4*14+8*6-16), R29
+#else
+	SUBU	$(4*14-16), R29	// For soft-float, no FPR.
+#endif
 	MOVW	R5, (4*1)(R29)
 	MOVW	R6, (4*2)(R29)
 	MOVW	R7, (4*3)(R29)
@@ -34,14 +38,14 @@ TEXT crosscall2(SB),NOSPLIT,$-4
 	MOVW	R23, (4*11)(R29)
 	MOVW	g, (4*12)(R29)
 	MOVW	R31, (4*13)(R29)
-
+#ifndef GOMIPS_softfloat
 	MOVD	F20, (4*14)(R29)
 	MOVD	F22, (4*14+8*1)(R29)
 	MOVD	F24, (4*14+8*2)(R29)
 	MOVD	F26, (4*14+8*3)(R29)
 	MOVD	F28, (4*14+8*4)(R29)
 	MOVD	F30, (4*14+8*5)(R29)
-
+#endif
 	JAL	runtime·load_g(SB)
 	JAL	(R4)
 
@@ -55,7 +59,7 @@ TEXT crosscall2(SB),NOSPLIT,$-4
 	MOVW	(4*11)(R29), R23
 	MOVW	(4*12)(R29), g
 	MOVW	(4*13)(R29), R31
-
+#ifndef GOMIPS_softfloat
 	MOVD	(4*14)(R29), F20
 	MOVD	(4*14+8*1)(R29), F22
 	MOVD	(4*14+8*2)(R29), F24
@@ -64,4 +68,7 @@ TEXT crosscall2(SB),NOSPLIT,$-4
 	MOVD	(4*14+8*5)(R29), F30
 
 	ADDU	$(4*14+8*6-16), R29
+#else
+	ADDU	$(4*14-16), R29
+#endif
 	RET

src/runtime/cgo/gcc_mipsx.S

@@ -14,8 +14,11 @@
 .globl crosscall1
 .set noat
 crosscall1:
+#ifndef __mips_soft_float
 	addiu	$29, $29, -88
-
+#else
+	addiu	$29, $29, -40 // For soft-float, no need to make room for FP registers
+#endif
 	sw	$31, 0($29)
 	sw	$16, 4($29)
 	sw	$17, 8($29)
@@ -27,14 +30,14 @@ crosscall1:
 	sw	$23, 32($29)
 	sw	$30, 36($29)
 
+#ifndef __mips_soft_float
 	sdc1	$f20, 40($29)
 	sdc1	$f22, 48($29)
 	sdc1	$f24, 56($29)
 	sdc1	$f26, 64($29)
 	sdc1	$f28, 72($29)
 	sdc1	$f30, 80($29)
-
-
+#endif
 	move	$20, $4 // save R4
 	move	$4, $6
 	jalr	$5	// call setg_gcc
@@ -49,16 +52,20 @@ crosscall1:
 	lw	$22, 28($29)
 	lw	$23, 32($29)
 	lw	$30, 36($29)
+#ifndef __mips_soft_float
 	ldc1	$f20, 40($29)
 	ldc1	$f22, 48($29)
 	ldc1	$f24, 56($29)
 	ldc1	$f26, 64($29)
 	ldc1	$f28, 72($29)
 	ldc1	$f30, 80($29)
-
+#endif
 	lw	$31, 0($29)
-
+#ifndef __mips_soft_float
 	addiu	$29, $29, 88
+#else
+	addiu	$29, $29, 40
+#endif
 	jr	$31
 
 .set at