From 310f248c22c5a20eaa4de1e612af3338a89144f3 Mon Sep 17 00:00:00 2001
From: Tim Northover <Tim.Northover@arm.com>
Date: Tue, 20 Nov 2012 09:56:11 +0000
Subject: [PATCH] Fix physical register liveness calculations:

+ Take account of clobbers
+ Give outputs priority over inputs since they happen later.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@168360 91177308-0d34-0410-b5e6-96231b3b80d8
---
 include/llvm/CodeGen/MachineInstrBundle.h |  5 +----
 lib/CodeGen/MachineBasicBlock.cpp         | 15 +++++++++------
 lib/CodeGen/MachineInstrBundle.cpp        |  6 ++++--
 test/CodeGen/ARM/domain-conv-vmovs.ll     | 20 ++++++++++++++++++++
 4 files changed, 34 insertions(+), 12 deletions(-)

diff --git a/include/llvm/CodeGen/MachineInstrBundle.h b/include/llvm/CodeGen/MachineInstrBundle.h
index 854ba06209c..3c60ad1f295 100644
--- a/include/llvm/CodeGen/MachineInstrBundle.h
+++ b/include/llvm/CodeGen/MachineInstrBundle.h
@@ -149,16 +149,13 @@ public:
   /// PhysRegInfo - Information about a physical register used by a set of
   /// operands.
   struct PhysRegInfo {
-    /// Clobbers - Reg or an overlapping register is defined, or a regmask 
+    /// Clobbers - Reg or an overlapping register is defined, or a regmask
     /// clobbers Reg.
     bool Clobbers;
 
     /// Defines - Reg or a super-register is defined.
     bool Defines;
 
-    /// DefinesOverlap - Reg or an overlapping register is defined.
-    bool DefinesOverlap;
-
     /// Reads - Read or a super-register is read.
     bool Reads;
 
diff --git a/lib/CodeGen/MachineBasicBlock.cpp b/lib/CodeGen/MachineBasicBlock.cpp
index 18d021d521d..4406c89aba2 100644
--- a/lib/CodeGen/MachineBasicBlock.cpp
+++ b/lib/CodeGen/MachineBasicBlock.cpp
@@ -982,7 +982,6 @@ MachineBasicBlock::LivenessQueryResult
 MachineBasicBlock::computeRegisterLiveness(const TargetRegisterInfo *TRI,
                                            unsigned Reg, MachineInstr *MI,
                                            unsigned Neighborhood) {
-  
   unsigned N = Neighborhood;
   MachineBasicBlock *MBB = MI->getParent();
 
@@ -997,14 +996,18 @@ MachineBasicBlock::computeRegisterLiveness(const TargetRegisterInfo *TRI,
       MachineOperandIteratorBase::PhysRegInfo Analysis =
         MIOperands(I).analyzePhysReg(Reg, TRI);
 
-      if (Analysis.Kills)
+      if (Analysis.Defines)
+        // Outputs happen after inputs so they take precedence if both are
+        // present.
+        return Analysis.DefinesDead ? LQR_Dead : LQR_Live;
+
+      if (Analysis.Kills || Analysis.Clobbers)
         // Register killed, so isn't live.
         return LQR_Dead;
 
-      else if (Analysis.DefinesOverlap || Analysis.ReadsOverlap)
+      else if (Analysis.ReadsOverlap)
         // Defined or read without a previous kill - live.
-        return (Analysis.Defines || Analysis.Reads) ? 
-          LQR_Live : LQR_OverlappingLive;
+        return Analysis.Reads ? LQR_Live : LQR_OverlappingLive;
 
     } while (I != MBB->begin() && --N > 0);
   }
@@ -1036,7 +1039,7 @@ MachineBasicBlock::computeRegisterLiveness(const TargetRegisterInfo *TRI,
         return (Analysis.Reads) ?
           LQR_Live : LQR_OverlappingLive;
 
-      else if (Analysis.DefinesOverlap)
+      else if (Analysis.Clobbers || Analysis.Defines)
         // Defined (but not read) therefore cannot have been live.
         return LQR_Dead;
     }
diff --git a/lib/CodeGen/MachineInstrBundle.cpp b/lib/CodeGen/MachineInstrBundle.cpp
index 1f7fbfc719b..70f97dedaaa 100644
--- a/lib/CodeGen/MachineInstrBundle.cpp
+++ b/lib/CodeGen/MachineInstrBundle.cpp
@@ -281,7 +281,7 @@ MachineOperandIteratorBase::PhysRegInfo
 MachineOperandIteratorBase::analyzePhysReg(unsigned Reg,
                                            const TargetRegisterInfo *TRI) {
   bool AllDefsDead = true;
-  PhysRegInfo PRI = {false, false, false, false, false, false, false};
+  PhysRegInfo PRI = {false, false, false, false, false, false};
 
   assert(TargetRegisterInfo::isPhysicalRegister(Reg) &&
          "analyzePhysReg not given a physical register!");
@@ -305,7 +305,9 @@ MachineOperandIteratorBase::analyzePhysReg(unsigned Reg,
       // Reg or a super-reg is read, and perhaps killed also.
       PRI.Reads = true;
       PRI.Kills = MO.isKill();
-    } if (IsRegOrOverlapping && MO.readsReg()) {
+    }
+
+    if (IsRegOrOverlapping && MO.readsReg()) {
       PRI.ReadsOverlap = true;// Reg or an overlapping register is read.
     }
 
diff --git a/test/CodeGen/ARM/domain-conv-vmovs.ll b/test/CodeGen/ARM/domain-conv-vmovs.ll
index a5c41144584..0ebac94e137 100644
--- a/test/CodeGen/ARM/domain-conv-vmovs.ll
+++ b/test/CodeGen/ARM/domain-conv-vmovs.ll
@@ -98,3 +98,23 @@ define i32 @test_vmovs_no_sreg(i32 %in) {
 
   ret i32 %resi
 }
+
+
+; The point of this test is:
+;   + Make sure s1 is live before the BL
+;   + Make sure s1 is clobbered by the BL
+;   + Convince LLVM to emit a VMOV to S0
+;   + Convince LLVM to domain-convert this.
+
+; When all of those are satisfied, LLVM should *not* mark s1 as an implicit-use
+; because it's dead.
+
+declare float @clobbers_s1(float, float)
+
+define <2 x float> @test_clobbers_recognised(<2 x float> %invec, float %val) {
+  %elt = call float @clobbers_s1(float %val, float %val)
+
+  %vec = insertelement <2 x float> %invec, float %elt, i32 0
+  %res = fadd <2 x float> %vec, %vec
+  ret <2 x float> %res
+}
-- 
2.34.1