From 696d5d44214cb7215aa9431b7be0c9fa2ce161ca Mon Sep 17 00:00:00 2001
From: Hans Wennborg <hans@hanshq.net>
Date: Wed, 25 Jan 2017 17:14:48 +0000
Subject: [PATCH] Merging r293025:
 ------------------------------------------------------------------------
 r293025 | ahatanak | 2017-01-24 22:21:51 -0800 (Tue, 24 Jan 2017) | 29 lines

[SimplifyCFG] Do not sink and merge inline-asm instructions.

Conservatively disable sinking and merging inline-asm instructions as doing so
can potentially create arguments that cannot satisfy the inline-asm constraints.

For example, SimplifyCFG used to do the following transformation:

(before)
if.then:
  %0 = call i32 asm "rorl $2, $0", "=&r,0,n"(i32 %r6, i32 8)
  br label %if.end
if.else:
  %1 = call i32 asm "rorl $2, $0", "=&r,0,n"(i32 %r6, i32 6)
  br label %if.end

(after)
  %.sink = select i1 %tobool, i32 6, i32 8
  %0 = call i32 asm "rorl $2, $0", "=&r,0,n"(i32 %r6, i32 %.sink)

This would result in a crash in the backend since only immediate integer operands
are permitted for constraint "n".

rdar://problem/30110806

Differential Revision: https://reviews.llvm.org/D29111




------------------------------------------------------------------------


git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_40@293074 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Transforms/Utils/SimplifyCFG.cpp          |  8 +++++++
 .../SimplifyCFG/sink-common-code.ll           | 24 +++++++++++++++++++
 2 files changed, 32 insertions(+)

diff --git a/lib/Transforms/Utils/SimplifyCFG.cpp b/lib/Transforms/Utils/SimplifyCFG.cpp
index 6e30919246c..7b0bddbbb83 100644
--- a/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -1436,6 +1436,14 @@ static bool canSinkInstructions(
     if (isa<PHINode>(I) || I->isEHPad() || isa<AllocaInst>(I) ||
         I->getType()->isTokenTy())
       return false;
+
+    // Conservatively return false if I is an inline-asm instruction. Sinking
+    // and merging inline-asm instructions can potentially create arguments
+    // that cannot satisfy the inline-asm constraints.
+    if (const auto *C = dyn_cast<CallInst>(I))
+      if (C->isInlineAsm())
+        return false;
+
     // Everything must have only one use too, apart from stores which
     // have no uses.
     if (!isa<StoreInst>(I) && !I->hasOneUse())
diff --git a/test/Transforms/SimplifyCFG/sink-common-code.ll b/test/Transforms/SimplifyCFG/sink-common-code.ll
index 953d96edada..0f7bfa8516c 100644
--- a/test/Transforms/SimplifyCFG/sink-common-code.ll
+++ b/test/Transforms/SimplifyCFG/sink-common-code.ll
@@ -768,6 +768,30 @@ if.end:
 ; CHECK-NOT: exact
 ; CHECK: }
 
+; Check that simplifycfg doesn't sink and merge inline-asm instructions.
+
+define i32 @test_inline_asm1(i32 %c, i32 %r6) {
+entry:
+  %tobool = icmp eq i32 %c, 0
+  br i1 %tobool, label %if.else, label %if.then
+
+if.then:
+  %0 = call i32 asm "rorl $2, $0", "=&r,0,n,~{dirflag},~{fpsr},~{flags}"(i32 %r6, i32 8)
+  br label %if.end
+
+if.else:
+  %1 = call i32 asm "rorl $2, $0", "=&r,0,n,~{dirflag},~{fpsr},~{flags}"(i32 %r6, i32 6)
+  br label %if.end
+
+if.end:
+  %r6.addr.0 = phi i32 [ %0, %if.then ], [ %1, %if.else ]
+  ret i32 %r6.addr.0
+}
+
+; CHECK-LABEL: @test_inline_asm1(
+; CHECK: call i32 asm "rorl $2, $0", "=&r,0,n,~{dirflag},~{fpsr},~{flags}"(i32 %r6, i32 8)
+; CHECK: call i32 asm "rorl $2, $0", "=&r,0,n,~{dirflag},~{fpsr},~{flags}"(i32 %r6, i32 6)
+
 declare i32 @call_target()
 
 define void @test_operand_bundles(i1 %cond, i32* %ptr) {
-- 
2.50.0