[PATCH] D157655: [Mips] AttemptToFoldSymbolOffsetDifference: revert isMicroMips special case
Fangrui Song via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Thu Aug 10 14:36:52 PDT 2023
MaskRay created this revision.
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D52985 <https://reviews.llvm.org/D52985> added a .gcc_except_table workaround, but it doesn't match GNU
assembler.
void foo();
int bar() {
foo();
try { throw 1; }
catch (int) { return 1; }
return 0;
}
clang --target=mipsel-linux-gnu -mmicromips -S a.cc
mipsel-linux-gnu-gcc -mmicromips -c a.s -o gnu.o
.uleb128 ($cst_end0)-($cst_begin0) // bit 0 is not forced to 1
.uleb128 ($func_begin0)-($func_begin0) // bit 0 is not forced to 1
I have inspected `.gcc_except_table` output by `mipsel-linux-gnu-gcc -mmicromips -c a.cc`.
The `.uleb128` values are not forced to set the least significant bit.
Worse, PC-relative `.long func - .` values differ from GNU assembler.
The original intention of D52985 <https://reviews.llvm.org/D52985> seems unclear to me. I think whatever
goal it wants to achieve should be moved to an upper layer.
This isMicroMips special case has caused problems to fix MCAssembler::relaxLEB to use evaluateAsAbsolute instead of evaluateKnownAbsolute,
which is needed to proper support R_RISCV_SET_ULEB128/R_RISCV_SUB_ULEB128.
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D157655
Files:
llvm/lib/MC/MCExpr.cpp
llvm/test/CodeGen/Mips/micromips-b-range.ll
llvm/test/CodeGen/Mips/micromips-gcc-except-table.ll
llvm/test/DebugInfo/Mips/eh_frame.ll
Index: llvm/test/DebugInfo/Mips/eh_frame.ll
===================================================================
--- llvm/test/DebugInfo/Mips/eh_frame.ll
+++ llvm/test/DebugInfo/Mips/eh_frame.ll
@@ -26,9 +26,9 @@
; CHECK-READELF-PIC-NEXT: R_MIPS_PC32
; CHECK-READELF-NEXT: .gcc_except_table
-; EXCEPT-TABLE-STATIC: 0000 ff9b1501 0c011500 00150e23 01231e00 ...........#.#..
+; EXCEPT-TABLE-STATIC: 0000 ff9b1501 0c001400 00140e22 01221e00 ..........."."..
; EXCEPT-TABLE-STATIC: 0010 00010000 00000000
-; EXCEPT-TABLE-PIC: 0000 ff9b1501 0c012d00 002d133f 013f2a00 ......-..-.?.?*.
+; EXCEPT-TABLE-PIC: 0000 ff9b1501 0c002c00 002c123e 013e2a00 ......,..,.>.>*.
; EXCEPT-TABLE-PIC: 0010 00010000 00000000 ........
@_ZTIi = external constant ptr
Index: llvm/test/CodeGen/Mips/micromips-gcc-except-table.ll
===================================================================
--- llvm/test/CodeGen/Mips/micromips-gcc-except-table.ll
+++ llvm/test/CodeGen/Mips/micromips-gcc-except-table.ll
@@ -1,7 +1,7 @@
; RUN: llc -mtriple=mips-linux-gnu -mcpu=mips32r2 -mattr=+micromips -O3 -filetype=obj < %s | llvm-objdump -s -j .gcc_except_table - | FileCheck %s
; CHECK: Contents of section .gcc_except_table:
-; CHECK-NEXT: 0000 ff9b1501 0c011100 00110e1f 011f1800
+; CHECK-NEXT: 0000 ff9b1501 0c001000 00100e1e 011e1800
; CHECK-NEXT: 0010 00010000 00000000
@_ZTIi = external constant ptr
Index: llvm/test/CodeGen/Mips/micromips-b-range.ll
===================================================================
--- llvm/test/CodeGen/Mips/micromips-b-range.ll
+++ llvm/test/CodeGen/Mips/micromips-b-range.ll
@@ -13,7 +13,7 @@
; CHECK-NEXT: 1e: fb fd 00 00 sw $ra, 0($sp)
; CHECK-NEXT: 22: 41 a1 00 01 lui $1, 1
; CHECK-NEXT: 26: 40 60 00 02 bal 0x2e <foo+0x2e>
-; CHECK-NEXT: 2a: 30 21 04 69 addiu $1, $1, 1129
+; CHECK-NEXT: 2a: 30 21 04 68 addiu $1, $1, 1128
; CHECK-NEXT: 2e: 00 3f 09 50 addu $1, $ra, $1
; CHECK-NEXT: 32: ff fd 00 00 lw $ra, 0($sp)
; CHECK-NEXT: 36: 00 01 0f 3c jr $1
@@ -27,7 +27,7 @@
; CHECK-NEXT: 56: fb fd 00 00 sw $ra, 0($sp)
; CHECK-NEXT: 5a: 41 a1 00 01 lui $1, 1
; CHECK-NEXT: 5e: 40 60 00 02 bal 0x66 <foo+0x66>
-; CHECK-NEXT: 62: 30 21 04 5d addiu $1, $1, 1117
+; CHECK-NEXT: 62: 30 21 04 5c addiu $1, $1, 1116
; CHECK-NEXT: 66: 00 3f 09 50 addu $1, $ra, $1
; CHECK-NEXT: 6a: ff fd 00 00 lw $ra, 0($sp)
; CHECK-NEXT: 6e: 00 01 0f 3c jr $1
@@ -39,7 +39,7 @@
; CHECK-NEXT: 86: fb fd 00 00 sw $ra, 0($sp)
; CHECK-NEXT: 8a: 41 a1 00 01 lui $1, 1
; CHECK-NEXT: 8e: 40 60 00 02 bal 0x96 <foo+0x96>
-; CHECK-NEXT: 92: 30 21 04 2d addiu $1, $1, 1069
+; CHECK-NEXT: 92: 30 21 04 2c addiu $1, $1, 1068
; CHECK-NEXT: 96: 00 3f 09 50 addu $1, $ra, $1
; CHECK-NEXT: 9a: ff fd 00 00 lw $ra, 0($sp)
; CHECK-NEXT: 9e: 00 01 0f 3c jr $1
@@ -51,7 +51,7 @@
; CHECK-NEXT: 10476: fb fd 00 00 sw $ra, 0($sp)
; CHECK-NEXT: 1047a: 41 a1 00 01 lui $1, 1
; CHECK-NEXT: 1047e: 40 60 00 02 bal 0x10486 <foo+0x10486>
-; CHECK-NEXT: 10482: 30 21 04 01 addiu $1, $1, 1025
+; CHECK-NEXT: 10482: 30 21 04 00 addiu $1, $1, 1024
; CHECK-NEXT: 10486: 00 3f 09 50 addu $1, $ra, $1
; CHECK-NEXT: 1048a: ff fd 00 00 lw $ra, 0($sp)
; CHECK-NEXT: 1048e: 00 01 0f 3c jr $1
Index: llvm/lib/MC/MCExpr.cpp
===================================================================
--- llvm/lib/MC/MCExpr.cpp
+++ llvm/lib/MC/MCExpr.cpp
@@ -606,11 +606,6 @@
return;
auto FinalizeFolding = [&]() {
- // If symbol is labeled as micromips, we set low-bit to ensure
- // correct offset in .gcc_except_table
- if (Asm->getBackend().isMicroMips(&SA))
- Addend |= 1;
-
// Clear the symbol expr pointers to indicate we have folded these
// operands.
A = B = nullptr;
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