[RegisterCoalescer] Fix reuse of instruction pointers #1
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If a pointer gets recycled while it is already in a work list, it can cause duplicates in the work lists. In that case the same instruction may be processed twice. If it is coalesced the first time, processing it again would read deallocated memory. This is fixed by removing the first occurrence from the work lists when we detect a pointer was recycled. Fixes llvm#71178
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vvuksanovic
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Feb 9, 2024
…ing bound ops (llvm#80317) `getDataOperandBaseAddr` retrieve the address of a value when we need to generate bound operations. When switching to HLFIR, we did not really handle the fact that this value was then pointing to the result of a hlfir.declare. Because of that the `#1` value was being used. `#0` value is carrying the correct information about lowerbounds and should be used. This patch updates the `getDataOperandBaseAddr` function to use the correct result value from hlfir.declare.
vvuksanovic
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Aug 22, 2025
…vm#153560) Fixes llvm#153157 The proposed solution has been discussed here (llvm#153157 (comment)) This is what we would be seeing now ``` base) anutosh491@Anutoshs-MacBook-Air bin % ./lldb /Users/anutosh491/work/xeus-cpp/a.out (lldb) target create "/Users/anutosh491/work/xeus-cpp/a.out" Current executable set to '/Users/anutosh491/work/xeus-cpp/a.out' (arm64). (lldb) b main Breakpoint 1: where = a.out`main, address = 0x0000000100003f90 (lldb) r Process 71227 launched: '/Users/anutosh491/work/xeus-cpp/a.out' (arm64) Process 71227 stopped * thread #1, queue = 'com.apple.main-thread', stop reason = breakpoint 1.1 frame #0: 0x0000000100003f90 a.out`main a.out`main: -> 0x100003f90 <+0>: sub sp, sp, #0x10 0x100003f94 <+4>: str wzr, [sp, #0xc] 0x100003f98 <+8>: str w0, [sp, #0x8] 0x100003f9c <+12>: str x1, [sp] (lldb) expression --repl -l c -- 1> 1 + 1 (int) $0 = 2 2> 2 + 2 (int) $1 = 4 ``` ``` base) anutosh491@Anutoshs-MacBook-Air bin % ./lldb /Users/anutosh491/work/xeus-cpp/a.out (lldb) target create "/Users/anutosh491/work/xeus-cpp/a.out" Current executable set to '/Users/anutosh491/work/xeus-cpp/a.out' (arm64). (lldb) b main Breakpoint 1: where = a.out`main, address = 0x0000000100003f90 (lldb) r Process 71355 launched: '/Users/anutosh491/work/xeus-cpp/a.out' (arm64) Process 71355 stopped * thread #1, queue = 'com.apple.main-thread', stop reason = breakpoint 1.1 frame #0: 0x0000000100003f90 a.out`main a.out`main: -> 0x100003f90 <+0>: sub sp, sp, #0x10 0x100003f94 <+4>: str wzr, [sp, #0xc] 0x100003f98 <+8>: str w0, [sp, #0x8] 0x100003f9c <+12>: str x1, [sp] (lldb) expression --repl -l c -- 3 + 3 Warning: trailing input is ignored in --repl mode 1> 1 + 1 (int) $0 = 2 ```
vvuksanovic
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Aug 22, 2025
This can happen when JIT code is run, and we can't symbolize those
frames, but they should remain numbered in the stack. An example
spidermonkey trace:
```
#0 0x564ac90fb80f (/builds/worker/dist/bin/js+0x240e80f) (BuildId: 5d053c76aad4cfbd08259f8832e7ac78bbeeab58)
#1 0x564ac9223a64 (/builds/worker/dist/bin/js+0x2536a64) (BuildId: 5d053c76aad4cfbd08259f8832e7ac78bbeeab58)
llvm#2 0x564ac922316f (/builds/worker/dist/bin/js+0x253616f) (BuildId: 5d053c76aad4cfbd08259f8832e7ac78bbeeab58)
llvm#3 0x564ac9eac032 (/builds/worker/dist/bin/js+0x31bf032) (BuildId: 5d053c76aad4cfbd08259f8832e7ac78bbeeab58)
llvm#4 0x0dec477ca22e (<unknown module>)
```
Without this change, the following symbolization is output:
```
#0 0x55a6d72f980f in MOZ_CrashSequence /builds/worker/workspace/obj-build/dist/include/mozilla/Assertions.h:248:3
#1 0x55a6d72f980f in Crash(JSContext*, unsigned int, JS::Value*) /builds/worker/checkouts/gecko/js/src/shell/js.cpp:4223:5
llvm#2 0x55a6d7421a64 in CallJSNative(JSContext*, bool (*)(JSContext*, unsigned int, JS::Value*), js::CallReason, JS::CallArgs const&) /builds/worker/checkouts/gecko/js/src/vm/Interpreter.cpp:501:13
llvm#3 0x55a6d742116f in js::InternalCallOrConstruct(JSContext*, JS::CallArgs const&, js::MaybeConstruct, js::CallReason) /builds/worker/checkouts/gecko/js/src/vm/Interpreter.cpp:597:12
llvm#4 0x55a6d80aa032 in js::jit::DoCallFallback(JSContext*, js::jit::BaselineFrame*, js::jit::ICFallbackStub*, unsigned int, JS::Value*, JS::MutableHandle<JS::Value>) /builds/worker/checkouts/gecko/js/src/jit/BaselineIC.cpp:1705:10
llvm#4 0x2c803bd8f22e (<unknown module>)
```
The last frame has a duplicate number. With this change the numbering is
correct:
```
#0 0x5620c58ec80f in MOZ_CrashSequence /builds/worker/workspace/obj-build/dist/include/mozilla/Assertions.h:248:3
#1 0x5620c58ec80f in Crash(JSContext*, unsigned int, JS::Value*) /builds/worker/checkouts/gecko/js/src/shell/js.cpp:4223:5
llvm#2 0x5620c5a14a64 in CallJSNative(JSContext*, bool (*)(JSContext*, unsigned int, JS::Value*), js::CallReason, JS::CallArgs const&) /builds/worker/checkouts/gecko/js/src/vm/Interpreter.cpp:501:13
llvm#3 0x5620c5a1416f in js::InternalCallOrConstruct(JSContext*, JS::CallArgs const&, js::MaybeConstruct, js::CallReason) /builds/worker/checkouts/gecko/js/src/vm/Interpreter.cpp:597:12
llvm#4 0x5620c669d032 in js::jit::DoCallFallback(JSContext*, js::jit::BaselineFrame*, js::jit::ICFallbackStub*, unsigned int, JS::Value*, JS::MutableHandle<JS::Value>) /builds/worker/checkouts/gecko/js/src/jit/BaselineIC.cpp:1705:10
llvm#5 0x349f24c7022e (<unknown module>)
```
vvuksanovic
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Aug 22, 2025
…gic (llvm#153086) Given the test case: ```llvm define fastcc i16 @testbtst(i16 %a) nounwind { entry: switch i16 %a, label %no [ i16 11, label %yes i16 10, label %yes i16 9, label %yes i16 4, label %yes i16 3, label %yes i16 2, label %yes ] yes: ret i16 1 no: ret i16 0 } ``` We currently get this result: ```asm testbtst: ; @testbtst ; %bb.0: ; %entry move.l %d0, %d1 and.l llvm#65535, %d1 sub.l llvm#11, %d1 bhi .LBB0_3 ; %bb.1: ; %entry and.l llvm#65535, %d0 move.l llvm#3612, %d1 btst %d0, %d1 bne .LBB0_3 ; <------- Erroneous condition ; %bb.2: ; %yes moveq #1, %d0 rts .LBB0_3: ; %no moveq #0, %d0 rts ``` The cause of this is a line that explicitly reverses the `btst` condition code. But on M68k, `btst` sets condition codes the same as `and` with a bitmask, meaning `EQ` indicates failure (bit is zero) and not success, so the condition does not need to be reversed. In my testing, I've only been able to get switch statements to lower to `btst`, so I wasn't able to explicitly test other options for lowering. But (if possible to trigger) I believe they have the same logical error. For example, in `LowerAndToBTST()`, a comment specifies that it's lowering a case where the `and` result is compared against zero, which means the corresponding `btst` condition should also not be reversed. This patch simply flips the ternary expression in `getBitTestCondition()` to match the ISD condition code with the same M68k code, instead of the opposite.
vvuksanovic
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Aug 25, 2025
llvm#137975) An authenticated pointer can be explicitly checked by the compiler via a sequence of instructions that executes BRK on failure. It is important to recognize such BRK instruction as checking every register (as it is expected to immediately trigger an abnormal program termination) to prevent false positive reports about authentication oracles: autia x2, x3 autia x0, x1 ; neither x0 nor x2 are checked at this point eor x16, x0, x0, lsl #1 tbz x16, llvm#62, on_success ; marks x0 as checked ; end of BB: for x2 to be checked here, it must be checked in both ; successor basic blocks on_failure: brk 0xc470 on_success: ; x2 is checked ldr x1, [x2] ; marks x2 as checked
vvuksanovic
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Oct 6, 2025
Specifically, `X & M ?= C --> (C << clz(M)) ?= (X << clz(M))` where M is a non-empty sequence of ones starting at the least significant bit with the remainder zero and C is a constant subset of M that cannot be materialised into a SUBS (immediate). Proof: https://alive2.llvm.org/ce/z/haqdJ4. This improves the comparison in isinf, for example: ```cpp int isinf(float x) { return __builtin_isinf(x); } ``` Before: ``` isinf: fmov w9, s0 mov w8, #2139095040 and w9, w9, #0x7fffffff cmp w9, w8 cset w0, eq ret ``` After: ``` isinf: fmov w9, s0 mov w8, #-16777216 cmp w8, w9, lsl #1 cset w0, eq ret ```
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If a pointer gets recycled while it is already in a work list, it can cause duplicates in the work lists. In that case the same instruction may be processed twice. If it is coalesced the first time, processing it again would read deallocated memory. This is fixed by removing the first occurrence from the work lists when we detect a pointer was recycled.