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3a75cd4bf9
With this change, ideally IR pass can always generate llvm.stackguard call to get the stack guard; but for now there are still IR form stack guard customizations around (see getIRStackGuard()). Future SSP customization should go through LOAD_STACK_GUARD. There is a behavior change: stack guard values are not CSEed anymore, since we should never reuse the value in case that it has been spilled (and corrupted). See ssp-guard-spill.ll. This also cause the change of stack size and codegen in X86 and AArch64 test cases. Ideally we'd like to know if the guard created in llvm.stackprotector() gets spilled or not. If the value is spilled, discard the value and reload stack guard; otherwise reuse the value. This can be done by teaching register allocator to know how to rematerialize LOAD_STACK_GUARD and force a rematerialization (which seems hard), or check for spilling in expandPostRAPseudo. It only makes sense when the stack guard is a global variable, which requires more instructions to load. Anyway, this seems to go out of the scope of the current patch. llvm-svn: 266806
55 lines
1.7 KiB
LLVM
55 lines
1.7 KiB
LLVM
; RUN: llc < %s | FileCheck %s
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target triple = "x86_64-apple-macosx10.4.0"
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; __stack_chk_guard must be loaded for twice, once for setting up the canary,
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; another time for performing the check. It is because if we reuse the same
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; stack guard value, it may get spilled to the stack, then the for loop may
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; corrupt it.
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;
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; bool Bar(int*);
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; bool Foo(int n) {
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; int a[10];
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; for (int i = 0; i < n; i++) {
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; a[i] = 0;
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; }
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; return Bar(a);
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; }
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;
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; CHECK: movq ___stack_chk_guard
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; CHECK: movq ___stack_chk_guard
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define zeroext i1 @_Z3Fooi(i32 %n) sspstrong {
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entry:
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%n.addr = alloca i32, align 4
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%a = alloca [10 x i32], align 16
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%i = alloca i32, align 4
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store i32 %n, i32* %n.addr, align 4
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store i32 0, i32* %i, align 4
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br label %for.cond
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for.cond: ; preds = %for.inc, %entry
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%tmp = load i32, i32* %i, align 4
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%tmp1 = load i32, i32* %n.addr, align 4
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%cmp = icmp slt i32 %tmp, %tmp1
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br i1 %cmp, label %for.body, label %for.end
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for.body: ; preds = %for.cond
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%tmp2 = load i32, i32* %i, align 4
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%idxprom = sext i32 %tmp2 to i64
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%arrayidx = getelementptr inbounds [10 x i32], [10 x i32]* %a, i64 0, i64 %idxprom
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store i32 0, i32* %arrayidx, align 4
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br label %for.inc
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for.inc: ; preds = %for.body
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%tmp3 = load i32, i32* %i, align 4
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%inc = add nsw i32 %tmp3, 1
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store i32 %inc, i32* %i, align 4
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br label %for.cond
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for.end: ; preds = %for.cond
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%arraydecay = getelementptr inbounds [10 x i32], [10 x i32]* %a, i32 0, i32 0
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%call = call zeroext i1 @_Z3BarPi(i32* %arraydecay)
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ret i1 %call
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}
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declare zeroext i1 @_Z3BarPi(i32*)
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