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Commit dfa550a

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Mark Seaborn
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Fix llc to not reuse spill slots in functions that invoke setjmp()
We need to ensure that StackSlotColoring.cpp does not reuse stack spill slots in functions that call "returns_twice" functions such as setjmp(), otherwise this can lead to miscompiled code, because a stack slot would be clobbered when it's still live. This was already handled correctly for functions that call setjmp() (though this wasn't covered by a test), but not for functions that invoke setjmp(). We fix this by changing callsFunctionThatReturnsTwice() to check for invoke instructions. This fixes PR18244. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@199180 91177308-0d34-0410-b5e6-96231b3b80d8
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‎lib/IR/Function.cpp

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Original file line numberDiff line numberDiff line change
@@ -736,10 +736,8 @@ bool Function::isDefTriviallyDead() const {
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bool Function::callsFunctionThatReturnsTwice() const {
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for (const_inst_iterator
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I = inst_begin(this), E = inst_end(this); I != E; ++I) {
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const CallInst* callInst = dyn_cast<CallInst>(&*I);
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if (!callInst)
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continue;
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if (callInst->canReturnTwice())
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ImmutableCallSite CS(&*I);
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if (CS && CS.hasFnAttr(Attribute::ReturnsTwice))
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return true;
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}
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‎test/CodeGen/X86/setjmp-spills.ll

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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,141 @@
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; RUN: llc < %s -mtriple=i386-linux | FileCheck %s -check-prefix=X86-32
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; RUN: llc < %s -mtriple=x86_64-linux | FileCheck %s -check-prefix=X86-64
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declare i32 @get_val()
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declare void @use_val(i32)
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declare i1 @setjmp()
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declare void @longjmp()
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declare void @personality()
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; Test that llc avoids reusing spill slots in functions that call
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; setjmp(), whether they use "call" or "invoke" for calling setjmp()
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; (PR18244).
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define void @setjmp_caller() {
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; X86-32-LABEL: setjmp_caller:
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; X86-64-LABEL: setjmp_caller:
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; This code keeps enough variables live across the setjmp() call that
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; they don't all fit in registers and the compiler will allocate a
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; spill slot.
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%a1 = call i32 @get_val()
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%a2 = call i32 @get_val()
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%a3 = call i32 @get_val()
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%a4 = call i32 @get_val()
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%a5 = call i32 @get_val()
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%a6 = call i32 @get_val()
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%a7 = call i32 @get_val()
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%a8 = call i32 @get_val()
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; X86-32: movl %eax, [[SPILL_SLOT:[0-9]+]](%esp)
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; X86-32: calll get_val
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; X86-64: movl %eax, [[SPILL_SLOT:[0-9]+]](%rsp)
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; X86-64: callq get_val
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%setjmp_result = call i1 @setjmp() returns_twice
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br i1 %setjmp_result, label %second, label %first
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; X86-32: calll setjmp
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; X86-64: callq setjmp
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; Again, keep enough variables live that they need spill slots. Since
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; this function calls a returns_twice function (setjmp()), the
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; compiler should not reuse the spill slots. longjmp() can return to
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; where the first spill slots were still live.
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first:
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%b1 = call i32 @get_val()
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%b2 = call i32 @get_val()
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%b3 = call i32 @get_val()
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%b4 = call i32 @get_val()
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%b5 = call i32 @get_val()
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%b6 = call i32 @get_val()
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%b7 = call i32 @get_val()
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%b8 = call i32 @get_val()
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call void @use_val(i32 %b1)
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call void @use_val(i32 %b2)
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call void @use_val(i32 %b3)
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call void @use_val(i32 %b4)
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call void @use_val(i32 %b5)
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call void @use_val(i32 %b6)
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call void @use_val(i32 %b7)
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call void @use_val(i32 %b8)
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call void @longjmp()
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unreachable
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; X86-32-NOT: movl {{.*}}, [[SPILL_SLOT]](%esp)
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; X86-64-NOT: movl {{.*}}, [[SPILL_SLOT]](%rsp)
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second:
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call void @use_val(i32 %a1)
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call void @use_val(i32 %a2)
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call void @use_val(i32 %a3)
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call void @use_val(i32 %a4)
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call void @use_val(i32 %a5)
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call void @use_val(i32 %a6)
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call void @use_val(i32 %a7)
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call void @use_val(i32 %a8)
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ret void
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}
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; This is the same as above, but using "invoke" rather than "call" to
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; call setjmp().
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define void @setjmp_invoker() {
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; X86-32-LABEL: setjmp_invoker:
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; X86-64-LABEL: setjmp_invoker:
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%a1 = call i32 @get_val()
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%a2 = call i32 @get_val()
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%a3 = call i32 @get_val()
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%a4 = call i32 @get_val()
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%a5 = call i32 @get_val()
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%a6 = call i32 @get_val()
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%a7 = call i32 @get_val()
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%a8 = call i32 @get_val()
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; X86-32: movl %eax, [[SPILL_SLOT:[0-9]+]](%esp)
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; X86-32: calll get_val
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; X86-64: movl %eax, [[SPILL_SLOT:[0-9]+]](%rsp)
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; X86-64: callq get_val
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%setjmp_result = invoke i1 @setjmp() returns_twice
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to label %cont unwind label %lpad
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; X86-32: calll setjmp
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; X86-64: callq setjmp
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cont:
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br i1 %setjmp_result, label %second, label %first
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lpad:
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%lp = landingpad { i8*, i32 } personality void ()* @personality cleanup
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unreachable
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first:
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%b1 = call i32 @get_val()
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%b2 = call i32 @get_val()
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%b3 = call i32 @get_val()
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%b4 = call i32 @get_val()
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%b5 = call i32 @get_val()
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%b6 = call i32 @get_val()
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%b7 = call i32 @get_val()
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%b8 = call i32 @get_val()
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call void @use_val(i32 %b1)
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call void @use_val(i32 %b2)
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call void @use_val(i32 %b3)
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call void @use_val(i32 %b4)
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call void @use_val(i32 %b5)
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call void @use_val(i32 %b6)
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call void @use_val(i32 %b7)
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call void @use_val(i32 %b8)
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call void @longjmp()
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unreachable
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; X86-32-NOT: movl {{.*}}, [[SPILL_SLOT]](%esp)
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; X86-64-NOT: movl {{.*}}, [[SPILL_SLOT]](%rsp)
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second:
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call void @use_val(i32 %a1)
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call void @use_val(i32 %a2)
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call void @use_val(i32 %a3)
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call void @use_val(i32 %a4)
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call void @use_val(i32 %a5)
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call void @use_val(i32 %a6)
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call void @use_val(i32 %a7)
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call void @use_val(i32 %a8)
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ret void
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}

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