From 79a76a4e5516106136c45689f4796f5c93574a82 Mon Sep 17 00:00:00 2001
From: YunQiang Su <wzssyqa@gmail.com>
Date: Tue, 9 Jun 2020 04:09:58 +0000
Subject: [PATCH] [PATCH] cmd/go, cmd/cgo: pass -mfp32 and -mhard/soft-float to
 MIPS GCC

For mips32 currently, we are using FP32, while the gcc may be FPXX,
which may generate .MIPS.abiflags and .gnu.attributes section with
value as FPXX. So the kernel will treat the exe as FPXX, and may
choose to use FR=1 FPU mode for it.
Currently, in Go, we use 2 lwc1 to load both half of a double value
to a pair of even-odd FPR. This behavior can only work with FR=0 mode.

In FR=1 mode, all of 32 FPR are 64bit. If we lwc1 the high-half of a double
value to an odd FPR, and try to use the previous even FPR to compute, the
real high-half of even FPR will be unpredicatable.
We set -mfp32 to force the gcc generate FP32 code and section value.

More details about FP32/FPXX/FP64 are explained in:
https://web.archive.org/web/20180828210612/https://dmz-portal.mips.com/wiki/MIPS_O32_ABI_-_FR0_and_FR1_Interlinking

When GOMIPS/GOMIPS64 is set as softfloat, we should also pass
 -msoft-float to gcc.

Here we also add -mno-odd-spreg option, since Loongson's CPU cannot use
odd-number FR in FR=0 mode.

Fixes #39435

Change-Id: I54026ad416a815fe43a9261ebf6d02e5519c3930

Gbp-Pq: Name 0004-Mips32-cgo-use-mfp32-option.patch
---
 src/cmd/cgo/gcc.go               | 12 ++++++++++--
 src/cmd/cgo/main.go              |  4 +++-
 src/cmd/go/internal/work/exec.go | 14 ++++++++++++--
 3 files changed, 25 insertions(+), 5 deletions(-)

diff --git a/src/cmd/cgo/gcc.go b/src/cmd/cgo/gcc.go
index 7f99057a..dd69fd7e 100644
--- a/src/cmd/cgo/gcc.go
+++ b/src/cmd/cgo/gcc.go
@@ -1545,9 +1545,17 @@ func (p *Package) gccMachine() []string {
 	case "s390x":
 		return []string{"-m64"}
 	case "mips64", "mips64le":
-		return []string{"-mabi=64"}
+		if gomips64 == "hardfloat" {
+			return []string{"-mabi=64", "-mhard-float"}
+		} else if gomips64 == "softfloat" {
+			return []string{"-mabi=64", "-msoft-float"}
+		}
 	case "mips", "mipsle":
-		return []string{"-mabi=32"}
+		if gomips == "hardfloat" {
+			return []string{"-mabi=32", "-mfp32", "-mhard-float", "-mno-odd-spreg"}
+		} else if gomips == "softfloat" {
+			return []string{"-mabi=32", "-msoft-float"}
+		}
 	}
 	return nil
 }
diff --git a/src/cmd/cgo/main.go b/src/cmd/cgo/main.go
index 5a7bb3f8..e0fede83 100644
--- a/src/cmd/cgo/main.go
+++ b/src/cmd/cgo/main.go
@@ -227,7 +227,7 @@ var gccgoMangleCheckDone bool
 var gccgoNewmanglingInEffect bool
 var importRuntimeCgo = flag.Bool("import_runtime_cgo", true, "import runtime/cgo in generated code")
 var importSyscall = flag.Bool("import_syscall", true, "import syscall in generated code")
-var goarch, goos string
+var goarch, goos, gomips, gomips64 string
 
 func main() {
 	objabi.AddVersionFlag() // -V
@@ -376,6 +376,8 @@ func newPackage(args []string) *Package {
 	if s := os.Getenv("GOOS"); s != "" {
 		goos = s
 	}
+	gomips = objabi.GOMIPS
+	gomips64 = objabi.GOMIPS64
 	ptrSize := ptrSizeMap[goarch]
 	if ptrSize == 0 {
 		fatalf("unknown ptrSize for $GOARCH %q", goarch)
diff --git a/src/cmd/go/internal/work/exec.go b/src/cmd/go/internal/work/exec.go
index 25d15079..bdef08eb 100644
--- a/src/cmd/go/internal/work/exec.go
+++ b/src/cmd/go/internal/work/exec.go
@@ -2409,9 +2409,19 @@ func (b *Builder) gccArchArgs() []string {
 	case "s390x":
 		return []string{"-m64", "-march=z196"}
 	case "mips64", "mips64le":
-		return []string{"-mabi=64"}
+		args := []string{"-mabi=64"}
+		if cfg.GOMIPS64 == "hardfloat" {
+			return append(args, "-mhard-float")
+		} else if cfg.GOMIPS64 == "softfloat" {
+			return append(args, "-msoft-float")
+		}
 	case "mips", "mipsle":
-		return []string{"-mabi=32", "-march=mips32"}
+		args := []string{"-mabi=32", "-march=mips32"}
+		if cfg.GOMIPS == "hardfloat" {
+			return append(args, "-mhard-float", "-mfp32", "-mno-odd-spreg")
+		} else if cfg.GOMIPS == "softfloat" {
+			return append(args, "-msoft-float")
+		}
 	case "ppc64":
 		if cfg.Goos == "aix" {
 			return []string{"-maix64"}
-- 
2.30.2