From: Chandler Carruth <chandlerc@gmail.com>
Date: Mon, 23 Jul 2018 07:56:15 +0000 (+0000)
Subject: [x86/SLH] Fix a bug where we would harden tail calls twice -- once as
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=d0f4fb1b00cb9f52ccc92a67d0f34f1a2f28faeb;p=llvm

[x86/SLH] Fix a bug where we would harden tail calls twice -- once as
a call, and then again as a return.

Also added a comment to try and explain better why we would be doing
what we're doing when hardening the (non-call) returns.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@337673 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Target/X86/X86SpeculativeLoadHardening.cpp b/lib/Target/X86/X86SpeculativeLoadHardening.cpp
index c068507095a..3d2bbd3e55c 100644
--- a/lib/Target/X86/X86SpeculativeLoadHardening.cpp
+++ b/lib/Target/X86/X86SpeculativeLoadHardening.cpp
@@ -525,7 +525,11 @@ bool X86SpeculativeLoadHardeningPass::runOnMachineFunction(
         continue;
 
       MachineInstr &MI = MBB.back();
-      if (!MI.isReturn())
+
+      // We only care about returns that are not also calls. For calls, that
+      // happen to also be returns (tail calls) we will have already handled
+      // them as calls.
+      if (!MI.isReturn() || MI.isCall())
         continue;
 
       hardenReturnInstr(MI);
diff --git a/test/CodeGen/X86/speculative-load-hardening-indirect.ll b/test/CodeGen/X86/speculative-load-hardening-indirect.ll
index b067c10a254..33741ff7b75 100644
--- a/test/CodeGen/X86/speculative-load-hardening-indirect.ll
+++ b/test/CodeGen/X86/speculative-load-hardening-indirect.ll
@@ -37,9 +37,6 @@ define i32 @test_indirect_tail_call(i32 ()** %ptr) nounwind {
 ; X64-NEXT:    movq %rsp, %rax
 ; X64-NEXT:    movq $-1, %rcx
 ; X64-NEXT:    sarq $63, %rax
-; X64-NEXT:    movq %rax, %rcx
-; X64-NEXT:    shlq $47, %rcx
-; X64-NEXT:    orq %rcx, %rsp
 ; X64-NEXT:    shlq $47, %rax
 ; X64-NEXT:    orq %rax, %rsp
 ; X64-NEXT:    jmpq *(%rdi) # TAILCALL
@@ -77,9 +74,6 @@ define i32 @test_indirect_tail_call_global() nounwind {
 ; X64-NEXT:    movq %rsp, %rax
 ; X64-NEXT:    movq $-1, %rcx
 ; X64-NEXT:    sarq $63, %rax
-; X64-NEXT:    movq %rax, %rcx
-; X64-NEXT:    shlq $47, %rcx
-; X64-NEXT:    orq %rcx, %rsp
 ; X64-NEXT:    shlq $47, %rax
 ; X64-NEXT:    orq %rax, %rsp
 ; X64-NEXT:    jmpq *{{.*}}(%rip) # TAILCALL