c41a212712
I found that when I enable ThinLTO, a miscompilation triggers that had
been hidden all the time previously. The bug appears to happen as
follows:
1. TinyGo generates a function with a runtime.trackPointer call, but
without an alloca (or the alloca gets optimized away).
2. LLVM sees that no alloca needs to be kept alive across the
runtime.trackPointer call, and therefore it adds the 'tail' flag.
One of the effects of this flag is that it makes it undefined
behavior to keep allocas alive across the call (which is still safe
at that point).
3. The GC lowering pass adds a stack slot alloca and converts
runtime.trackPointer calls into alloca stores.
The last step triggers the bug: the compiler inserts an alloca where
there was none before but that's not valid as long as the 'tail' flag is
present.
This patch fixes the bug in a somewhat dirty way, by always creating a
dummy alloca so that LLVM won't do the optimization in step 2 (and
possibly other optimizations that rely on there being no alloca
instruction).
96 строки
3 КиБ
LLVM
96 строки
3 КиБ
LLVM
; ModuleID = 'float.go'
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source_filename = "float.go"
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target datalayout = "e-m:e-p:32:32-p10:8:8-p20:8:8-i64:64-n32:64-S128-ni:1:10:20"
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target triple = "wasm32-unknown-wasi"
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declare noalias nonnull ptr @runtime.alloc(i32, ptr, ptr) #0
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declare void @runtime.trackPointer(ptr nocapture readonly, ptr, ptr) #0
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; Function Attrs: nounwind
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define hidden void @main.init(ptr %context) unnamed_addr #1 {
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entry:
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ret void
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}
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; Function Attrs: nounwind
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define hidden i32 @main.f32tou32(float %v, ptr %context) unnamed_addr #1 {
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entry:
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%positive = fcmp oge float %v, 0.000000e+00
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%withinmax = fcmp ole float %v, 0x41EFFFFFC0000000
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%inbounds = and i1 %positive, %withinmax
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%saturated = sext i1 %positive to i32
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%normal = fptoui float %v to i32
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%0 = select i1 %inbounds, i32 %normal, i32 %saturated
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ret i32 %0
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}
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; Function Attrs: nounwind
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define hidden float @main.maxu32f(ptr %context) unnamed_addr #1 {
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entry:
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ret float 0x41F0000000000000
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}
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; Function Attrs: nounwind
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define hidden i32 @main.maxu32tof32(ptr %context) unnamed_addr #1 {
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entry:
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ret i32 -1
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}
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; Function Attrs: nounwind
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define hidden { i32, i32, i32, i32 } @main.inftoi32(ptr %context) unnamed_addr #1 {
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entry:
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ret { i32, i32, i32, i32 } { i32 -1, i32 0, i32 2147483647, i32 -2147483648 }
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}
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; Function Attrs: nounwind
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define hidden i32 @main.u32tof32tou32(i32 %v, ptr %context) unnamed_addr #1 {
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entry:
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%0 = uitofp i32 %v to float
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%withinmax = fcmp ole float %0, 0x41EFFFFFC0000000
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%normal = fptoui float %0 to i32
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%1 = select i1 %withinmax, i32 %normal, i32 -1
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ret i32 %1
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}
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; Function Attrs: nounwind
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define hidden float @main.f32tou32tof32(float %v, ptr %context) unnamed_addr #1 {
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entry:
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%positive = fcmp oge float %v, 0.000000e+00
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%withinmax = fcmp ole float %v, 0x41EFFFFFC0000000
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%inbounds = and i1 %positive, %withinmax
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%saturated = sext i1 %positive to i32
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%normal = fptoui float %v to i32
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%0 = select i1 %inbounds, i32 %normal, i32 %saturated
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%1 = uitofp i32 %0 to float
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ret float %1
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}
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; Function Attrs: nounwind
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define hidden i8 @main.f32tou8(float %v, ptr %context) unnamed_addr #1 {
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entry:
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%positive = fcmp oge float %v, 0.000000e+00
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%withinmax = fcmp ole float %v, 2.550000e+02
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%inbounds = and i1 %positive, %withinmax
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%saturated = sext i1 %positive to i8
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%normal = fptoui float %v to i8
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%0 = select i1 %inbounds, i8 %normal, i8 %saturated
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ret i8 %0
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}
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; Function Attrs: nounwind
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define hidden i8 @main.f32toi8(float %v, ptr %context) unnamed_addr #1 {
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entry:
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%abovemin = fcmp oge float %v, -1.280000e+02
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%belowmax = fcmp ole float %v, 1.270000e+02
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%inbounds = and i1 %abovemin, %belowmax
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%saturated = select i1 %abovemin, i8 127, i8 -128
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%isnan = fcmp uno float %v, 0.000000e+00
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%remapped = select i1 %isnan, i8 0, i8 %saturated
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%normal = fptosi float %v to i8
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%0 = select i1 %inbounds, i8 %normal, i8 %remapped
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ret i8 %0
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}
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attributes #0 = { "target-features"="+bulk-memory,+nontrapping-fptoint,+sign-ext" }
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attributes #1 = { nounwind "target-features"="+bulk-memory,+nontrapping-fptoint,+sign-ext" }
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