From 96e65783957e8ca3c5eb305f4bd2822e4edb31e8 Mon Sep 17 00:00:00 2001
From: Ulrich Weigand <ulrich.weigand@de.ibm.com>
Date: Thu, 20 Jun 2013 16:23:52 +0000
Subject: [PowerPC] Optimize @ha/@l constructs

This patch adds support for having the assembler optimize fixups
to constructs like "symbol@ha" or "symbol@l" if "symbol" can be
resolved at assembler time.

This optimization is already present in the PPCMCExpr.cpp code
for handling PPC_HA16/PPC_LO16 target expressions.  However,
those target expression were used only on Darwin targets.

This patch changes target expression code so that they are
usable also with the GNU assembler (using the @ha / @l syntax
instead of the ha16() / lo16() syntax), and changes the
MCInst lowering code to generate those target expressions
where appropriate.

It also changes the asm parser to generate HA16/LO16 target
expressions when parsing assembler source that uses the
@ha / @l modifiers.  The effect is that now the above-
mentioned optimization automatically becomes available
for those situations too.


llvm-svn: 184436
---
 llvm/lib/Target/PowerPC/AsmParser/PPCAsmParser.cpp | 92 +++++++++++++++++++++-
 1 file changed, 91 insertions(+), 1 deletion(-)

(limited to 'llvm/lib/Target/PowerPC/AsmParser')

diff --git a/llvm/lib/Target/PowerPC/AsmParser/PPCAsmParser.cpp b/llvm/lib/Target/PowerPC/AsmParser/PPCAsmParser.cpp
index 9cf16f08aed..59a5ef9a535 100644
--- a/llvm/lib/Target/PowerPC/AsmParser/PPCAsmParser.cpp
+++ b/llvm/lib/Target/PowerPC/AsmParser/PPCAsmParser.cpp
@@ -8,6 +8,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "MCTargetDesc/PPCMCTargetDesc.h"
+#include "MCTargetDesc/PPCMCExpr.h"
 #include "llvm/MC/MCTargetAsmParser.h"
 #include "llvm/MC/MCStreamer.h"
 #include "llvm/MC/MCExpr.h"
@@ -126,6 +127,10 @@ class PPCAsmParser : public MCTargetAsmParser {
 
   virtual bool ParseRegister(unsigned &RegNo, SMLoc &StartLoc, SMLoc &EndLoc);
 
+  const MCExpr *ExtractModifierFromExpr(const MCExpr *E,
+                                        PPCMCExpr::VariantKind &Variant);
+  bool ParseExpression(const MCExpr *&EVal);
+
   bool ParseOperand(SmallVectorImpl<MCParsedAsmOperand*> &Operands);
 
   bool ParseDirectiveWord(unsigned Size, SMLoc L);
@@ -540,6 +545,91 @@ ParseRegister(unsigned &RegNo, SMLoc &StartLoc, SMLoc &EndLoc) {
   return Error(StartLoc, "invalid register name");
 }
 
+/// Extract @l/@ha modifier from expression.  Recursively scan
+/// the expression and check for VK_PPC_ADDR16_HA/VK_PPC_ADDR16_LO
+/// symbol variants.  If all symbols with modifier use the same
+/// variant, return the corresponding PPCMCExpr::VariantKind,
+/// and a modified expression using the default symbol variant.
+/// Otherwise, return NULL.
+const MCExpr *PPCAsmParser::
+ExtractModifierFromExpr(const MCExpr *E,
+                        PPCMCExpr::VariantKind &Variant) {
+  MCContext &Context = getParser().getContext();
+  Variant = PPCMCExpr::VK_PPC_None;
+
+  switch (E->getKind()) {
+  case MCExpr::Target:
+  case MCExpr::Constant:
+    return 0;
+
+  case MCExpr::SymbolRef: {
+    const MCSymbolRefExpr *SRE = cast<MCSymbolRefExpr>(E);
+
+    switch (SRE->getKind()) {
+    case MCSymbolRefExpr::VK_PPC_ADDR16_HA:
+      Variant = PPCMCExpr::VK_PPC_HA16;
+      break;
+    case MCSymbolRefExpr::VK_PPC_ADDR16_LO:
+      Variant = PPCMCExpr::VK_PPC_LO16;
+      break;
+    default:
+      return 0;
+    }
+
+    return MCSymbolRefExpr::Create(&SRE->getSymbol(), Context);
+  }
+
+  case MCExpr::Unary: {
+    const MCUnaryExpr *UE = cast<MCUnaryExpr>(E);
+    const MCExpr *Sub = ExtractModifierFromExpr(UE->getSubExpr(), Variant);
+    if (!Sub)
+      return 0;
+    return MCUnaryExpr::Create(UE->getOpcode(), Sub, Context);
+  }
+
+  case MCExpr::Binary: {
+    const MCBinaryExpr *BE = cast<MCBinaryExpr>(E);
+    PPCMCExpr::VariantKind LHSVariant, RHSVariant;
+    const MCExpr *LHS = ExtractModifierFromExpr(BE->getLHS(), LHSVariant);
+    const MCExpr *RHS = ExtractModifierFromExpr(BE->getRHS(), RHSVariant);
+
+    if (!LHS && !RHS)
+      return 0;
+
+    if (!LHS) LHS = BE->getLHS();
+    if (!RHS) RHS = BE->getRHS();
+
+    if (LHSVariant == PPCMCExpr::VK_PPC_None)
+      Variant = RHSVariant;
+    else if (RHSVariant == PPCMCExpr::VK_PPC_None)
+      Variant = LHSVariant;
+    else if (LHSVariant == RHSVariant)
+      Variant = LHSVariant;
+    else
+      return 0;
+
+    return MCBinaryExpr::Create(BE->getOpcode(), LHS, RHS, Context);
+  }
+  }
+
+  llvm_unreachable("Invalid expression kind!");
+}
+
+/// Parse an expression.  This differs from the default "parseExpression"
+/// in that it handles complex @l/@ha modifiers.
+bool PPCAsmParser::
+ParseExpression(const MCExpr *&EVal) {
+  if (getParser().parseExpression(EVal))
+    return true;
+
+  PPCMCExpr::VariantKind Variant;
+  const MCExpr *E = ExtractModifierFromExpr(EVal, Variant);
+  if (E)
+    EVal = PPCMCExpr::Create(Variant, E, getParser().getContext());
+
+  return false;
+}
+
 bool PPCAsmParser::
 ParseOperand(SmallVectorImpl<MCParsedAsmOperand*> &Operands) {
   SMLoc S = Parser.getTok().getLoc();
@@ -571,7 +661,7 @@ ParseOperand(SmallVectorImpl<MCParsedAsmOperand*> &Operands) {
   case AsmToken::Identifier:
   case AsmToken::Dot:
   case AsmToken::Dollar:
-    if (!getParser().parseExpression(EVal))
+    if (!ParseExpression(EVal))
       break;
     /* fall through */
   default:
-- 
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