[go] cmd/link: modify the register used in trampoline

[Meidan Li (Gerrit)]

Meidan Li has uploaded the change for review

Commit message

cmd/link: modify the register used in trampoline

Change-Id: Ie7bba0caa30a764a45bcb47635c35c829036c5a2

Change diff

diff --git a/src/cmd/internal/obj/loong64/doc.go b/src/cmd/internal/obj/loong64/doc.go
index 19c9e05..80ded5f 100644
--- a/src/cmd/internal/obj/loong64/doc.go
+++ b/src/cmd/internal/obj/loong64/doc.go
@@ -6,6 +6,18 @@
 Package loong64 implements an LoongArch64 assembler. Go assembly syntax is different from
 GNU LoongArch64 syntax, but we can still follow the general rules to map between them.
 
+# Register Convention
+
+	Name            |  Alias  | Meaning
+	-------------------------------------------------------------------------------------------------------------------
+	R0              | REGZERO | Constant zero
+	R1              | REGLINK | Return address
+	R3              | REGSP   | Stack pointer
+	R12,R13,R14,R15 |         | For plt and trampoline, use with caution in assembly code, save before calling function
+	R22             | REGG    | Goroutine pointer
+	R29             | REGCTXT | Context for closures
+	R30             | REGTMP  | Tmp register used by assembler
+
 # Instructions mnemonics mapping rules
 
 1. Bit widths represented by various instruction suffixes and prefixes
diff --git a/src/cmd/link/internal/loong64/asm.go b/src/cmd/link/internal/loong64/asm.go
index dfcf928..a87a93e 100644
--- a/src/cmd/link/internal/loong64/asm.go
+++ b/src/cmd/link/internal/loong64/asm.go
@@ -645,13 +645,6 @@
 	r := relocs.At(ri)
 	switch r.Type() {
 	case objabi.ElfRelocOffset + objabi.RelocType(elf.R_LARCH_B26), objabi.R_CALLLOONG64:
-		if ldr.SymType(rs) == sym.SDYNIMPORT {
-			// Nothing to do.
-			// The plt symbol has not been added. If we add tramp
-			// here, plt will not work.
-			return
-		}
-
 		var t int64
 		// ldr.SymValue(rs) == 0 indicates a cross-package jump to a function that is not yet
 		// laid out. Conservatively use a trampoline. This should be rare, as we lay out packages
@@ -720,7 +713,7 @@
 	tramp.SetSize(12) // 3 instructions
 	P := make([]byte, tramp.Size())
 
-	o1 := uint32(0x1a00001e) // pcalau12i $r30, 0
+	o1 := uint32(0x1a00000f) // pcalau12i $r15, 0
 	ctxt.Arch.ByteOrder.PutUint32(P, o1)
 	r1, _ := tramp.AddRel(objabi.R_LOONG64_ADDR_HI)
 	r1.SetOff(0)
@@ -728,7 +721,7 @@
 	r1.SetSym(target)
 	r1.SetAdd(offset)
 
-	o2 := uint32(0x02c003de) // addi.d $r30, $r30, 0
+	o2 := uint32(0x02c001ef) // addi.d $r15, $r15, 0
 	ctxt.Arch.ByteOrder.PutUint32(P[4:], o2)
 	r2, _ := tramp.AddRel(objabi.R_LOONG64_ADDR_LO)
 	r2.SetOff(4)
@@ -736,7 +729,7 @@
 	r2.SetSym(target)
 	r2.SetAdd(offset)
 
-	o3 := uint32(0x4c0003c0) // jirl $r0, $r30, 0
+	o3 := uint32(0x4c0001e0) // jirl $r0, $r15, 0
 	ctxt.Arch.ByteOrder.PutUint32(P[8:], o3)
 
 	tramp.SetData(P)
@@ -746,21 +739,21 @@
 	tramp.SetSize(12) // 3 instructions
 	P := make([]byte, tramp.Size())
 
-	o1 := uint32(0x1a00001e) // pcalau12i $r30, 0
+	o1 := uint32(0x1a00000f) // pcalau12i $r15, 0
 	ctxt.Arch.ByteOrder.PutUint32(P, o1)
 	r1, _ := tramp.AddRel(objabi.R_LOONG64_GOT_HI)
 	r1.SetOff(0)
 	r1.SetSiz(4)
 	r1.SetSym(target)
 
-	o2 := uint32(0x28c003de) // ld.d $r30, $r30, 0
+	o2 := uint32(0x28c001ef) // ld.d $r15, $r15, 0
 	ctxt.Arch.ByteOrder.PutUint32(P[4:], o2)
 	r2, _ := tramp.AddRel(objabi.R_LOONG64_GOT_LO)
 	r2.SetOff(4)
 	r2.SetSiz(4)
 	r2.SetSym(target)
 
-	o3 := uint32(0x4c0003c0) // jirl $r0, $r30, 0
+	o3 := uint32(0x4c0001e0) // jirl $r0, $r15, 0
 	ctxt.Arch.ByteOrder.PutUint32(P[8:], o3)
 
 	tramp.SetData(P)

Change information

Files:

• M src/cmd/internal/obj/loong64/doc.go
• M src/cmd/link/internal/loong64/asm.go

Change size: S

Delta: 2 files changed, 18 insertions(+), 13 deletions(-)

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Gerrit-Change-Number: 726140

Gerrit-PatchSet: 1

Gerrit-Owner: Meidan Li <lime...@loongson.cn>

[Meidan Li (Gerrit)]

Attention needed from Cherry Mui, Ian Lance Taylor and Russ Cox

Meidan Li uploaded new patchset

Meidan Li uploaded patch set #2 to this change.

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Gerrit-PatchSet: 2

Gerrit-Owner: Meidan Li <lime...@loongson.cn>

Gerrit-Reviewer: Cherry Mui <cher...@google.com>

Gerrit-Reviewer: Ian Lance Taylor <ia...@golang.org>

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