void updated this revision to Diff 228762.
void added a comment.
Herald added subscribers: llvm-commits, hiraditya.
Herald added a project: LLVM.
Analyze "asm goto" for initialized variables.
An "asm goto" statement is a terminator and thus doesn't indicate variable
assignments like normal inline assembly. Handle them specially.
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D69876/new/
https://reviews.llvm.org/D69876
Files:
llvm/docs/LangRef.rst
llvm/lib/AsmParser/LLParser.cpp
llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
llvm/lib/IR/Verifier.cpp
llvm/test/CodeGen/X86/callbr-asm-outputs.ll
llvm/test/CodeGen/X86/callbr-asm.ll
Index: llvm/test/CodeGen/X86/callbr-asm.ll
===================================================================
--- llvm/test/CodeGen/X86/callbr-asm.ll
+++ llvm/test/CodeGen/X86/callbr-asm.ll
@@ -131,3 +131,54 @@
%1 = load i32, i32* %a.addr, align 4
ret i32 %1
}
+
+define i32 @test4(i32 %out1, i32 %out2) {
+; Test 4 - asm-goto with output constraints.
+; CHECK-LABEL: test4:
+; CHECK: # %bb.0: # %entry
+; CHECK-NEXT: movl $-1, %eax
+; CHECK-NEXT: movl 4(%esp), %ecx
+; CHECK-NEXT: #APP
+; CHECK-NEXT: testl %ecx, %ecx
+; CHECK-NEXT: testl %edx, %ecx
+; CHECK-NEXT: jne .Ltmp5
+; CHECK-NEXT: #NO_APP
+; CHECK-NEXT: .LBB3_1:
+; CHECK-NEXT: #APP
+; CHECK-NEXT: testl %ecx, %edx
+; CHECK-NEXT: testl %ecx, %edx
+; CHECK-NEXT: jne .Ltmp6
+; CHECK-NEXT: #NO_APP
+; CHECK-NEXT: .LBB3_2:
+; CHECK-NEXT: addl %edx, %ecx
+; CHECK-NEXT: movl %ecx, %eax
+; CHECK-NEXT: retl
+; CHECK-NEXT: .Ltmp5:
+; CHECK-NEXT: .LBB3_3:
+; CHECK-NEXT: movl $-2, %eax
+; CHECK-NEXT: .Ltmp6:
+; CHECK-NEXT: .LBB3_4:
+; CHECK-NEXT: retl
+entry:
+ %0 = callbr { i32, i32 } asm sideeffect "testl $0, $0; testl $1, $2; jne ${3:l}", "=r,=r,r,X,X,~{dirflag},~{fpsr},~{flags}"(i32 %out1, i8* blockaddress(@test4, %label_true), i8* blockaddress(@test4, %return))
+ to label %asm.fallthrough [label %label_true, label %return]
+
+asm.fallthrough: ; preds = %entry
+ %asmresult = extractvalue { i32, i32 } %0, 0
+ %asmresult1 = extractvalue { i32, i32 } %0, 1
+ %1 = callbr { i32, i32 } asm sideeffect "testl $0, $1; testl $2, $3; jne ${5:l}", "=r,=r,r,r,X,X,~{dirflag},~{fpsr},~{flags}"(i32 %asmresult, i32 %asmresult1, i8* blockaddress(@test4, %label_true), i8* blockaddress(@test4, %return))
+ to label %asm.fallthrough2 [label %label_true, label %return]
+
+asm.fallthrough2: ; preds = %asm.fallthrough
+ %asmresult3 = extractvalue { i32, i32 } %1, 0
+ %asmresult4 = extractvalue { i32, i32 } %1, 1
+ %add = add nsw i32 %asmresult3, %asmresult4
+ br label %return
+
+label_true: ; preds = %asm.fallthrough, %entry
+ br label %return
+
+return: ; preds = %entry, %asm.fallthrough, %label_true, %asm.fallthrough2
+ %retval.0 = phi i32 [ %add, %asm.fallthrough2 ], [ -2, %label_true ], [ -1, %asm.fallthrough ], [ -1, %entry ]
+ ret i32 %retval.0
+}
Index: llvm/test/CodeGen/X86/callbr-asm-outputs.ll
===================================================================
--- llvm/test/CodeGen/X86/callbr-asm-outputs.ll
+++ llvm/test/CodeGen/X86/callbr-asm-outputs.ll
@@ -1,18 +1,26 @@
-; RUN: not llc -mtriple=i686-- < %s 2> %t
-; RUN: FileCheck %s < %t
+; RUN: llc -mtriple=i686-- < %s | FileCheck %s
-; CHECK: error: asm-goto outputs not supported
+; A test for asm-goto output
-; A test for asm-goto output prohibition
-
-define i32 @test(i32 %a) {
+; CHECK-LABEL: test1:
+; CHECK: movl 4(%esp), %eax
+; CHECK-NEXT: addl $4, %eax
+; CHECK-NEXT: #APP
+; CHECK-NEXT: xorl %eax, %eax
+; CHECK-NEXT: jmp .Ltmp0
+; CHECK-NEXT: #NO_APP
+; CHECK-NEXT: .LBB0_1:
+; CHECK-NEXT: retl
+; CHECK-NEXT: .Ltmp0:
+define i32 @test1(i32 %x) {
entry:
- %0 = add i32 %a, 4
- %1 = callbr i32 asm "xorl $1, $1; jmp ${1:l}", "=&r,r,X,~{dirflag},~{fpsr},~{flags}"(i32 %0, i8* blockaddress(@test, %fail)) to label %normal [label %fail]
+ %add = add nsw i32 %x, 4
+ %ret = callbr i32 asm "xorl $1, $0; jmp ${2:l}", "=r,r,X,~{dirflag},~{fpsr},~{flags}"(i32 %add, i8* blockaddress(@test1, %abnormal))
+ to label %normal [label %abnormal]
normal:
- ret i32 %1
+ ret i32 %ret
-fail:
+abnormal:
ret i32 1
}
Index: llvm/lib/IR/Verifier.cpp
===================================================================
--- llvm/lib/IR/Verifier.cpp
+++ llvm/lib/IR/Verifier.cpp
@@ -2492,8 +2492,6 @@
void Verifier::visitCallBrInst(CallBrInst &CBI) {
Assert(CBI.isInlineAsm(), "Callbr is currently only used for asm-goto!",
&CBI);
- Assert(CBI.getType()->isVoidTy(), "Callbr return value is not supported!",
- &CBI);
for (unsigned i = 0, e = CBI.getNumSuccessors(); i != e; ++i)
Assert(CBI.getSuccessor(i)->getType()->isLabelTy(),
"Callbr successors must all have pointer type!", &CBI);
Index: llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
===================================================================
--- llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -2834,6 +2834,7 @@
assert(isa<InlineAsm>(I.getCalledValue()) &&
"Only know how to handle inlineasm callbr");
visitInlineAsm(&I);
+ CopyToExportRegsIfNeeded(&I);
// Retrieve successors.
MachineBasicBlock *Return = FuncInfo.MBBMap[I.getDefaultDest()];
Index: llvm/lib/AsmParser/LLParser.cpp
===================================================================
--- llvm/lib/AsmParser/LLParser.cpp
+++ llvm/lib/AsmParser/LLParser.cpp
@@ -6416,9 +6416,6 @@
/*IsCall=*/true))
return true;
- if (isa<InlineAsm>(Callee) && !Ty->getReturnType()->isVoidTy())
- return Error(RetTypeLoc, "asm-goto outputs not supported");
-
// Set up the Attribute for the function.
SmallVector<Value *, 8> Args;
SmallVector<AttributeSet, 8> ArgAttrs;
Index: llvm/docs/LangRef.rst
===================================================================
--- llvm/docs/LangRef.rst
+++ llvm/docs/LangRef.rst
@@ -7096,14 +7096,14 @@
::
<result> = callbr [cconv] [ret attrs] [addrspace(<num>)] <ty>|<fnty> <fnptrval>(<function args>) [fn attrs]
- [operand bundles] to label <normal label> [other labels]
+ [operand bundles] to label <fallthrough label> [indirect labels]
Overview:
"""""""""
The '``callbr``' instruction causes control to transfer to a specified
function, with the possibility of control flow transfer to either the
-'``normal``' label or one of the '``other``' labels.
+'``fallthrough``' label or one of the '``indirect``' labels.
This instruction should only be used to implement the "goto" feature of gcc
style inline assembly. Any other usage is an error in the IR verifier.
@@ -7130,17 +7130,17 @@
type can be omitted if the function is not varargs.
#. '``fnptrval``': An LLVM value containing a pointer to a function to
be called. In most cases, this is a direct function call, but
- indirect ``callbr``'s are just as possible, calling an arbitrary pointer
+ other ``callbr``'s are just as possible, calling an arbitrary pointer
to function value.
#. '``function args``': argument list whose types match the function
signature argument types and parameter attributes. All arguments must
be of :ref:`first class <t_firstclass>` type. If the function signature
indicates the function accepts a variable number of arguments, the
extra arguments can be specified.
-#. '``normal label``': the label reached when the called function
- executes a '``ret``' instruction.
-#. '``other labels``': the labels reached when a callee transfers control
- to a location other than the normal '``normal label``'. The blockaddress
+#. '``fallthrough label``': the label reached when the inline assembly's
+ execution exits the bottom.
+#. '``indirect labels``': the labels reached when a callee transfers control
+ to a location other than the '``fallthrough label``'. The blockaddress
constant for these should also be in the list of '``function args``'.
#. The optional :ref:`function attributes <fnattrs>` list.
#. The optional :ref:`operand bundles <opbundles>` list.
@@ -7153,6 +7153,13 @@
establishes an association with additional labels to define where control
flow goes after the call.
+Outputs of a '``callbr``' instruction are valid only on the '``fallthrough``'
+path. Use of outputs on the '``indirect``' path(s) results in :ref:`poison
+values <poisonvalues>`. Care should be taken if the '``fallthrough``' block is
+also listed in the '``indirect``' blocks. The outputs may or may not result in
+:ref:`poison values <poisonvalues>` depending on the behavior of the inline
+assembly.
+
The only use of this today is to implement the "goto" feature of gcc inline
assembly where additional labels can be provided as locations for the inline
assembly to jump to.
@@ -7160,10 +7167,15 @@
Example:
""""""""
-.. code-block:: text
+.. code-block:: llvm
- callbr void asm "", "r,x"(i32 %x, i8 *blockaddress(@foo, %fail))
- to label %normal [label %fail]
+ ; "asm goto" without output constraints.
+ callbr void asm "", "r,X"(i32 %x, i8 *blockaddress(@foo, %indirect))
+ to label %fallthrough [label %indirect]
+
+ ; "asm goto" with output constraints.
+ <result> = callbr i32 asm "", "=r,r,X"(i32 %x, i8 *blockaddress(@foo, %indirect))
+ to label %fallthrough [label %indirect]
.. _i_resume:
_______________________________________________
cfe-commits mailing list
cfe-commits@lists.llvm.org
https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
