Decent gains for ARM Holdings, Associated British Foods and Rolls-Royce were providing a boost to London's stock market on Tuesday morning, offsetting relative weakness in the heavyweight mining sector.Miners were under pressure early on after a disappointing reading of Chinese manufacturing. The HSBC purchasing managers' index fell from 51.6 to 50.5 in April, worse than the fall to 51.5 expected.This follows last week's revelation of surprise slowdown in China in the first quarter, as economic growth fell to 7.7% in the first three months, worse forecasts for an acceleration to 8.0%."This was driven by a drop in the number of new orders, with the biggest concern being the drop in new orders for export, driven by an ongoing slowdown in the global economy," explained Market Analyst Craig Erlam from Alpari.He said that China could see further slowing in the second quarter, meaning that 7.7% growth "may already be looking out of reach".There is likely to be some element of caution amongst traders this week ahead of economic growth figures from the UK and US on Thursday and Friday, respectively. Consensus estimates are for a 0.1% expansion in UK gross domestic product in the first quarter and 3.1% growth in the States.FTSE 100: ARM provides a liftChip designer ARM Holdings surged early on after smashing both revenue and profit forecasts in the first quarter and saying that full-year results will be "at least" in line with current market estimates. The firm said that its first-quarter performance was fuelled by robust licensing and record royalty revenue.Associated British Foods edged higher after reporting a 10% rise in half-year revenue driven by sales at its clothing retail subsidiary Primark. Power solutions giant Rolls-Royce was also in demand after reaching an agreement to sell its 50% stake in the RTM322 helicopter engine programme to Turbomeca for €293m.Heading the other way were the miners as metals prices declined on the back of the poor Chinese data. Antofagasta, Rio Tinto, Fresnillo and Anglo American were among the worst performers. However, ENRC was bucking the trend, rebounding after heavy falls yesterday. Tullow Oil was also in the red as it revealed that it had plugged and abandoned a well offshore French Guiana after it failed to encounter any hydrocarbons. This was the latest in a string of disappointing operational updates from the FTSE 100-listed oil explorer.Utilities peers SSE and National Grid were also out of favour after Bank of America Merrill Lynch downgraded both stocks to 'neutral'.FTSE 250: AVEVA gains on upbeat guidanceEngineering data and IT group AVEVA Group was a high riser after saying that it expects to hit revenue and profit forecasts for the full year following good demand in its second half. Sanlam Securities released a research report this morning saying that the in-line trading update prompted it to move its rating from 'sell' to 'hold'. Premier Oil was also firmly higher after discovering oil at the Bonneville exploration well and its side track on the Catcher licence in the UK Central North Sea.FTSE 100 - RisersARM Holdings (ARM) 935.00p +7.59%Eurasian Natural Resources Corp. (ENRC) 290.10p +2.11%Aberdeen Asset Management (ADN) 405.70p +1.88%IMI (IMI) 1,181.00p +1.46%Associated British Foods (ABF) 1,876.00p +1.41%Burberry Group (BRBY) 1,297.00p +1.41%International Consolidated Airlines Group SA (CDI) (IAG) 259.80p +1.33%Compass Group (CPG) 826.50p +1.22%Rexam (REX) 518.50p +1.17%Wolseley (WOS) 3,121.00p +1.13%FTSE 100 - FallersRandgold Resources Ltd. (RRS) 4,810.00p -1.23%Vodafone Group (VOD) 192.75p -1.05%Anglo American (AAL) 1,577.50p -0.94%Antofagasta (ANTO) 885.00p -0.84%Admiral Group (ADM) 1,317.00p -0.75%Pearson (PSON) 1,116.00p -0.71%Evraz (EVR) 154.00p -0.71%National Grid (NG.) 792.50p -0.63%SSE (SSE) 1,523.00p -0.52%London Stock Exchange Group (LSE) 1,290.00p -0.39%FTSE 250 - RisersAveva Group (AVV) 2,150.00p +4.22%Premier Oil (PMO) 364.40p +3.79%Spectris (SXS) 1,945.00p +3.46%Savills (SVS) 527.00p +3.13%Dixons Retail (DXNS) 37.83p +2.22%Anite (AIE) 117.40p +2.09%Synthomer (SYNT) 182.50p +2.01%Imagination Technologies Group (IMG) 433.10p +2.00%William Hill (WMH) 418.20p +1.95%Electrocomponents (ECM) 233.20p +1.92%FTSE 250 - FallersBooker Group (BOK) 115.70p -3.18%African Barrick Gold (ABG) 182.80p -3.02%NMC Health (NMC) 333.60p -1.88%Kenmare Resources (KMR) 26.30p -1.61%KCOM Group (KCOM) 81.95p -1.56%Hochschild Mining (HOC) 236.50p -1.46%SDL (SDL) 379.40p -1.43%BH Global Ltd. USD Shares (BHGU) 11.85 -1.25%Bank of Georgia Holdings (BGEO) 1,512.00p -1.18%Devro (DVO) 305.40p -1.17%BC