From: Chris Lattner <sabre@nondot.org>
Date: Mon, 15 Nov 2004 23:16:34 +0000 (+0000)
Subject: Simplify and rearrange long shift code
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=36c625d3a597bc0126c06ce0ca5ddfe261b6bf60;p=oota-llvm.git

Simplify and rearrange long shift code


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@17861 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Target/X86/X86ISelSimple.cpp b/lib/Target/X86/X86ISelSimple.cpp
index 4e9e54261c3..e890e6bb2f9 100644
--- a/lib/Target/X86/X86ISelSimple.cpp
+++ b/lib/Target/X86/X86ISelSimple.cpp
@@ -2979,23 +2979,28 @@ void X86ISel::emitShiftOperation(MachineBasicBlock *MBB,
                   DestReg).addReg(SrcReg  ).addReg(SrcReg+1).addImm(Amount);
           BuildMI(*MBB, IP, Opc[2],2,DestReg+1).addReg(SrcReg+1).addImm(Amount);
         }
-      } else {                 // Shifting more than 32 bits
-        Amount -= 32;
+      } else if (Amount == 32) {
         if (isLeftShift) {
-          if (Amount != 0) {
-            BuildMI(*MBB, IP, X86::SHL32ri, 2,
-                    DestReg + 1).addReg(SrcReg).addImm(Amount);
-          } else {
-            BuildMI(*MBB, IP, X86::MOV32rr, 1, DestReg+1).addReg(SrcReg);
-          }
+          BuildMI(*MBB, IP, X86::MOV32rr, 1, DestReg+1).addReg(SrcReg);
           BuildMI(*MBB, IP, X86::MOV32ri, 1, DestReg).addImm(0);
         } else {
-          if (Amount != 0) {
-            BuildMI(*MBB, IP, isSigned ? X86::SAR32ri : X86::SHR32ri, 2,
-                    DestReg).addReg(SrcReg+1).addImm(Amount);
+          BuildMI(*MBB, IP, X86::MOV32rr, 1, DestReg).addReg(SrcReg);
+          if (!isSigned) {
+            BuildMI(*MBB, IP, X86::MOV32ri, 1, DestReg+1).addImm(0);
           } else {
-            BuildMI(*MBB, IP, X86::MOV32rr, 1, DestReg).addReg(SrcReg+1);
+            BuildMI(*MBB, IP, X86::SAR32ri, 2,
+                    DestReg+1).addReg(SrcReg).addImm(31);
           }
+        }
+      } else {                 // Shifting more than 32 bits
+        Amount -= 32;
+        if (isLeftShift) {
+          BuildMI(*MBB, IP, X86::SHL32ri, 2,
+                  DestReg + 1).addReg(SrcReg).addImm(Amount);
+          BuildMI(*MBB, IP, X86::MOV32ri, 1, DestReg).addImm(0);
+        } else {
+          BuildMI(*MBB, IP, isSigned ? X86::SAR32ri : X86::SHR32ri, 2,
+                  DestReg).addReg(SrcReg+1).addImm(Amount);
           BuildMI(*MBB, IP, X86::MOV32ri, 1, DestReg+1).addImm(0);
         }
       }