From: Cherry Mui <cherryyz@google.com>
Date: Sat, 13 Nov 2021 00:53:28 +0000 (-0500)
Subject: cmd/compile, runtime: mark R1 as clobbered for write barrier call
X-Git-Tag: go1.18beta1~326
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=ce4a2755956a42aa3211c121139a52c9a97a9aa0;p=gostls13.git

cmd/compile, runtime: mark R1 as clobbered for write barrier call

If the call to gcWriteBarrier is via PLT, the PLT stub will
clobber R1. Mark R1 clobbered.

For #49386.

Change-Id: I72df5bb3b8d10381fec5c567b15749aaf7d2ad70
Reviewed-on: https://go-review.googlesource.com/c/go/+/363698
Trust: Cherry Mui <cherryyz@google.com>
Run-TryBot: Cherry Mui <cherryyz@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
---

diff --git a/src/cmd/compile/internal/ssa/gen/S390XOps.go b/src/cmd/compile/internal/ssa/gen/S390XOps.go
index cd7bad7acb..eef8a2557c 100644
--- a/src/cmd/compile/internal/ssa/gen/S390XOps.go
+++ b/src/cmd/compile/internal/ssa/gen/S390XOps.go
@@ -509,8 +509,9 @@ func init() {
 
 		// LoweredWB invokes runtime.gcWriteBarrier. arg0=destptr, arg1=srcptr, arg2=mem, aux=runtime.gcWriteBarrier
 		// It saves all GP registers if necessary,
-		// but clobbers R14 (LR) because it's a call.
-		{name: "LoweredWB", argLength: 3, reg: regInfo{inputs: []regMask{buildReg("R2"), buildReg("R3")}, clobbers: (callerSave &^ gpg) | buildReg("R14")}, clobberFlags: true, aux: "Sym", symEffect: "None"},
+		// but clobbers R14 (LR) because it's a call,
+		// and also clobbers R1 as the PLT stub does.
+		{name: "LoweredWB", argLength: 3, reg: regInfo{inputs: []regMask{buildReg("R2"), buildReg("R3")}, clobbers: (callerSave &^ gpg) | buildReg("R14") | r1}, clobberFlags: true, aux: "Sym", symEffect: "None"},
 
 		// There are three of these functions so that they can have three different register inputs.
 		// When we check 0 <= c <= cap (A), then 0 <= b <= c (B), then 0 <= a <= b (C), we want the
diff --git a/src/cmd/compile/internal/ssa/opGen.go b/src/cmd/compile/internal/ssa/opGen.go
index 2038575b0c..81fe5d4c23 100644
--- a/src/cmd/compile/internal/ssa/opGen.go
+++ b/src/cmd/compile/internal/ssa/opGen.go
@@ -32779,7 +32779,7 @@ var opcodeTable = [...]opInfo{
 				{0, 4}, // R2
 				{1, 8}, // R3
 			},
-			clobbers: 4294918144, // R14 F0 F1 F2 F3 F4 F5 F6 F7 F8 F9 F10 F11 F12 F13 F14 F15
+			clobbers: 4294918146, // R1 R14 F0 F1 F2 F3 F4 F5 F6 F7 F8 F9 F10 F11 F12 F13 F14 F15
 		},
 	},
 	{
diff --git a/src/runtime/asm_s390x.s b/src/runtime/asm_s390x.s
index 5894fe5783..9159a67372 100644
--- a/src/runtime/asm_s390x.s
+++ b/src/runtime/asm_s390x.s
@@ -777,13 +777,12 @@ TEXT ·checkASM(SB),NOSPLIT,$0-1
 // gcWriteBarrier does NOT follow the Go ABI. It takes two arguments:
 // - R2 is the destination of the write
 // - R3 is the value being written at R2.
-// It clobbers R10 (the temp register).
+// It clobbers R10 (the temp register) and R1 (used by PLT stub).
 // It does not clobber any other general-purpose registers,
 // but may clobber others (e.g., floating point registers).
-TEXT runtime·gcWriteBarrier(SB),NOSPLIT,$104
+TEXT runtime·gcWriteBarrier(SB),NOSPLIT,$96
 	// Save the registers clobbered by the fast path.
-	MOVD	R1, 96(R15)
-	MOVD	R4, 104(R15)
+	MOVD	R4, 96(R15)
 	MOVD	g_m(g), R1
 	MOVD	m_p(R1), R1
 	// Increment wbBuf.next position.
@@ -798,8 +797,7 @@ TEXT runtime·gcWriteBarrier(SB),NOSPLIT,$104
 	// Is the buffer full?
 	CMPBEQ	R4, R1, flush
 ret:
-	MOVD	96(R15), R1
-	MOVD	104(R15), R4
+	MOVD	96(R15), R4
 	// Do the write.
 	MOVD	R3, (R2)
 	RET