[release-branch.go1.14] cmd/compile, runtime: mark R12 clobbered for write barrier call on PPC64
When external linking, for large binaries, the external linker
may insert a trampoline for the write barrier call, which looks
0000000005a98cc8 <__long_branch_runtime.gcWriteBarrier>:
5a98cc8: 86 01 82 3d addis r12,r2,390
5a98ccc: d8 bd 8c e9 ld r12,-16936(r12)
5a98cd0: a6 03 89 7d mtctr r12
5a98cd4: 20 04 80 4e bctr
It clobbers R12 (and CTR, which is never live across a call).
As at compile time we don't know whether the binary is big and
what link mode will be used, I think we need to mark R12 as
clobbered for write barrier call. For extra safety (future-proof)
we mark caller-saved register that cannot be used for function
arguments, which includes R11, as potentially clobbered as well.
Updates #40851.
Fixes #40938.
Change-Id: Iedd901c5072f1127cc59b0a48cfeb4aaec81b519
Reviewed-on: https://go-review.googlesource.com/c/go/+/248917
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Austin Clements <austin@google.com>
(cherry picked from commit b58d29741650c7bf10b17f455666e2727e1cdd2e)
Reviewed-on: https://go-review.googlesource.com/c/go/+/249697
diff --git a/src/cmd/compile/internal/ssa/gen/PPC64Ops.go b/src/cmd/compile/internal/ssa/gen/PPC64Ops.go
index ab671a2..d657957 100644
--- a/src/cmd/compile/internal/ssa/gen/PPC64Ops.go
+++ b/src/cmd/compile/internal/ssa/gen/PPC64Ops.go
@@ -561,9 +561,9 @@
{name: "LoweredAtomicOr8", argLength: 3, reg: gpstore, asm: "OR", faultOnNilArg0: true, hasSideEffects: true},
// LoweredWB invokes runtime.gcWriteBarrier. arg0=destptr, arg1=srcptr, arg2=mem, aux=runtime.gcWriteBarrier
- // It preserves R0 through R15, g, and its arguments R20 and R21,
+ // It preserves R0 through R17 (except special registers R1, R2, R11, R12, R13), g, and its arguments R20 and R21,
// but may clobber anything else, including R31 (REGTMP).
- {name: "LoweredWB", argLength: 3, reg: regInfo{inputs: []regMask{buildReg("R20"), buildReg("R21")}, clobbers: (callerSave &^ buildReg("R0 R3 R4 R5 R6 R7 R8 R9 R10 R11 R12 R14 R15 R20 R21 g")) | buildReg("R31")}, clobberFlags: true, aux: "Sym", symEffect: "None"},
+ {name: "LoweredWB", argLength: 3, reg: regInfo{inputs: []regMask{buildReg("R20"), buildReg("R21")}, clobbers: (callerSave &^ buildReg("R0 R3 R4 R5 R6 R7 R8 R9 R10 R14 R15 R16 R17 R20 R21 g")) | buildReg("R31")}, 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 dd05eec..be3f5ee 100644
--- a/src/cmd/compile/internal/ssa/opGen.go
+++ b/src/cmd/compile/internal/ssa/opGen.go
@@ -24940,7 +24940,7 @@
{0, 1048576}, // R20
{1, 2097152}, // R21
},
- clobbers: 576460746931503104, // R16 R17 R18 R19 R22 R23 R24 R25 R26 R27 R28 R29 R31 F1 F2 F3 F4 F5 F6 F7 F8 F9 F10 F11 F12 F13 F14 F15 F16 F17 F18 F19 F20 F21 F22 F23 F24 F25 F26
+ clobbers: 576460746931312640, // R11 R12 R18 R19 R22 R23 R24 R25 R26 R27 R28 R29 R31 F1 F2 F3 F4 F5 F6 F7 F8 F9 F10 F11 F12 F13 F14 F15 F16 F17 F18 F19 F20 F21 F22 F23 F24 F25 F26
},
},
{
diff --git a/src/runtime/asm_ppc64x.s b/src/runtime/asm_ppc64x.s
index 11d2f2f..23387a2 100644
--- a/src/runtime/asm_ppc64x.s
+++ b/src/runtime/asm_ppc64x.s
@@ -916,23 +916,23 @@
// - R20 is the destination of the write
// - R21 is the value being written at R20.
// It clobbers condition codes.
-// It does not clobber R0 through R15,
+// It does not clobber R0 through R17 (except special registers),
// but may clobber any other register, *including* R31.
TEXT runtime·gcWriteBarrier(SB),NOSPLIT,$112
// The standard prologue clobbers R31.
- // We use R16 and R17 as scratch registers.
- MOVD g_m(g), R16
- MOVD m_p(R16), R16
- MOVD (p_wbBuf+wbBuf_next)(R16), R17
+ // We use R18 and R19 as scratch registers.
+ MOVD g_m(g), R18
+ MOVD m_p(R18), R18
+ MOVD (p_wbBuf+wbBuf_next)(R18), R19
// Increment wbBuf.next position.
- ADD $16, R17
- MOVD R17, (p_wbBuf+wbBuf_next)(R16)
- MOVD (p_wbBuf+wbBuf_end)(R16), R16
- CMP R16, R17
+ ADD $16, R19
+ MOVD R19, (p_wbBuf+wbBuf_next)(R18)
+ MOVD (p_wbBuf+wbBuf_end)(R18), R18
+ CMP R18, R19
// Record the write.
- MOVD R21, -16(R17) // Record value
- MOVD (R20), R16 // TODO: This turns bad writes into bad reads.
- MOVD R16, -8(R17) // Record *slot
+ MOVD R21, -16(R19) // Record value
+ MOVD (R20), R18 // TODO: This turns bad writes into bad reads.
+ MOVD R18, -8(R19) // Record *slot
// Is the buffer full? (flags set in CMP above)
BEQ flush
ret:
@@ -956,11 +956,12 @@
MOVD R8, (FIXED_FRAME+56)(R1)
MOVD R9, (FIXED_FRAME+64)(R1)
MOVD R10, (FIXED_FRAME+72)(R1)
- MOVD R11, (FIXED_FRAME+80)(R1)
- MOVD R12, (FIXED_FRAME+88)(R1)
+ // R11, R12 may be clobbered by external-linker-inserted trampoline
// R13 is REGTLS
- MOVD R14, (FIXED_FRAME+96)(R1)
- MOVD R15, (FIXED_FRAME+104)(R1)
+ MOVD R14, (FIXED_FRAME+80)(R1)
+ MOVD R15, (FIXED_FRAME+88)(R1)
+ MOVD R16, (FIXED_FRAME+96)(R1)
+ MOVD R17, (FIXED_FRAME+104)(R1)
// This takes arguments R20 and R21.
CALL runtime·wbBufFlush(SB)
@@ -975,10 +976,10 @@
MOVD (FIXED_FRAME+56)(R1), R8
MOVD (FIXED_FRAME+64)(R1), R9
MOVD (FIXED_FRAME+72)(R1), R10
- MOVD (FIXED_FRAME+80)(R1), R11
- MOVD (FIXED_FRAME+88)(R1), R12
- MOVD (FIXED_FRAME+96)(R1), R14
- MOVD (FIXED_FRAME+104)(R1), R15
+ MOVD (FIXED_FRAME+80)(R1), R14
+ MOVD (FIXED_FRAME+88)(R1), R15
+ MOVD (FIXED_FRAME+96)(R1), R16
+ MOVD (FIXED_FRAME+104)(R1), R17
JMP ret
// Note: these functions use a special calling convention to save generated code space.
